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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a "Depends", "Recommends", or
480 "Build-Depends" relationship on a non-<em>main</em>
484 must not be so buggy that we refuse to support them,
488 must meet all policy requirements presented in this
497 <heading>The contrib archive area</heading>
500 Every package in <em>contrib</em> must comply with the DFSG.
504 In addition, the packages in <em>contrib</em>
505 <list compact="compact">
507 must not be so buggy that we refuse to support them,
511 must meet all policy requirements presented in this
519 Examples of packages which would be included in
520 <em>contrib</em> are:
521 <list compact="compact">
523 free packages which require <em>contrib</em>,
524 <em>non-free</em> packages or packages which are not
525 in our archive at all for compilation or execution,
529 wrapper packages or other sorts of free accessories for
536 <sect1 id="non-free">
537 <heading>The non-free archive area</heading>
540 Packages must be placed in <em>non-free</em> if they are
541 not compliant with the DFSG or are encumbered by patents
542 or other legal issues that make their distribution
547 In addition, the packages in <em>non-free</em>
548 <list compact="compact">
550 must not be so buggy that we refuse to support them,
554 must meet all policy requirements presented in this
555 manual that it is possible for them to meet.
557 It is possible that there are policy
558 requirements which the package is unable to
559 meet, for example, if the source is
560 unavailable. These situations will need to be
561 handled on a case-by-case basis.
570 <sect id="pkgcopyright">
571 <heading>Copyright considerations</heading>
574 Every package must be accompanied by a verbatim copy of its
575 copyright information and distribution license in the file
576 <file>/usr/share/doc/<var>package</var>/copyright</file>
577 (see <ref id="copyrightfile"> for further details).
581 We reserve the right to restrict files from being included
582 anywhere in our archives if
583 <list compact="compact">
585 their use or distribution would break a law,
588 there is an ethical conflict in their distribution or
592 we would have to sign a license for them, or
595 their distribution would conflict with other project
602 Programs whose authors encourage the user to make
603 donations are fine for the main distribution, provided
604 that the authors do not claim that not donating is
605 immoral, unethical, illegal or something similar; in such
606 a case they must go in <em>non-free</em>.
610 Packages whose copyright permission notices (or patent
611 problems) do not even allow redistribution of binaries
612 only, and where no special permission has been obtained,
613 must not be placed on the Debian FTP site and its mirrors
618 Note that under international copyright law (this applies
619 in the United States, too), <em>no</em> distribution or
620 modification of a work is allowed without an explicit
621 notice saying so. Therefore a program without a copyright
622 notice <em>is</em> copyrighted and you may not do anything
623 to it without risking being sued! Likewise if a program
624 has a copyright notice but no statement saying what is
625 permitted then nothing is permitted.
629 Many authors are unaware of the problems that restrictive
630 copyrights (or lack of copyright notices) can cause for
631 the users of their supposedly-free software. It is often
632 worthwhile contacting such authors diplomatically to ask
633 them to modify their license terms. However, this can be a
634 politically difficult thing to do and you should ask for
635 advice on the <tt>debian-legal</tt> mailing list first, as
640 When in doubt about a copyright, send mail to
641 <email>debian-legal@lists.debian.org</email>. Be prepared
642 to provide us with the copyright statement. Software
643 covered by the GPL, public domain software and BSD-like
644 copyrights are safe; be wary of the phrases "commercial
645 use prohibited" and "distribution restricted".
649 <sect id="subsections">
650 <heading>Sections</heading>
653 The packages in the archive areas <em>main</em>,
654 <em>contrib</em> and <em>non-free</em> are grouped further into
655 <em>sections</em> to simplify handling.
659 The archive area and section for each package should be
660 specified in the package's <tt>Section</tt> control record (see
661 <ref id="f-Section">). However, the maintainer of the Debian
662 archive may override this selection to ensure the consistency of
663 the Debian distribution. The <tt>Section</tt> field should be
665 <list compact="compact">
667 <em>section</em> if the package is in the
668 <em>main</em> archive area,
671 <em>area/section</em> if the package is in
672 the <em>contrib</em> or <em>non-free</em>
679 The Debian archive maintainers provide the authoritative
680 list of sections. At present, they are:
681 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
682 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
683 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
684 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
685 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
686 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
687 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
688 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
689 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
690 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
691 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
692 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
693 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
694 <em>zope</em>. The additional section <em>debian-installer</em>
695 contains special packages used by the installer and is not used
696 for normal Debian packages.
700 For more information about the sections and their definitions,
701 see the <url id="http://packages.debian.org/unstable/"
702 name="list of sections in unstable">.
706 <sect id="priorities">
707 <heading>Priorities</heading>
710 Each package should have a <em>priority</em> value, which is
711 included in the package's <em>control record</em>
712 (see <ref id="f-Priority">).
713 This information is used by the Debian package management tools to
714 separate high-priority packages from less-important packages.
718 The following <em>priority levels</em> are recognized by the
719 Debian package management tools.
721 <tag><tt>required</tt></tag>
723 Packages which are necessary for the proper
724 functioning of the system (usually, this means that
725 dpkg functionality depends on these packages).
726 Removing a <tt>required</tt> package may cause your
727 system to become totally broken and you may not even
728 be able to use <prgn>dpkg</prgn> to put things back,
729 so only do so if you know what you are doing. Systems
730 with only the <tt>required</tt> packages are probably
731 unusable, but they do have enough functionality to
732 allow the sysadmin to boot and install more software.
734 <tag><tt>important</tt></tag>
736 Important programs, including those which one would
737 expect to find on any Unix-like system. If the
738 expectation is that an experienced Unix person who
739 found it missing would say "What on earth is going on,
740 where is <prgn>foo</prgn>?", it must be an
741 <tt>important</tt> package.<footnote>
742 This is an important criterion because we are
743 trying to produce, amongst other things, a free
746 Other packages without which the system will not run
747 well or be usable must also have priority
748 <tt>important</tt>. This does
749 <em>not</em> include Emacs, the X Window System, TeX
750 or any other large applications. The
751 <tt>important</tt> packages are just a bare minimum of
752 commonly-expected and necessary tools.
754 <tag><tt>standard</tt></tag>
756 These packages provide a reasonably small but not too
757 limited character-mode system. This is what will be
758 installed by default if the user doesn't select anything
759 else. It doesn't include many large applications.
761 <tag><tt>optional</tt></tag>
763 (In a sense everything that isn't required is
764 optional, but that's not what is meant here.) This is
765 all the software that you might reasonably want to
766 install if you didn't know what it was and don't have
767 specialized requirements. This is a much larger system
768 and includes the X Window System, a full TeX
769 distribution, and many applications. Note that
770 optional packages should not conflict with each other.
772 <tag><tt>extra</tt></tag>
774 This contains all packages that conflict with others
775 with required, important, standard or optional
776 priorities, or are only likely to be useful if you
777 already know what they are or have specialized
778 requirements (such as packages containing only detached
785 Packages must not depend on packages with lower priority
786 values (excluding build-time dependencies). In order to
787 ensure this, the priorities of one or more packages may need
796 <heading>Binary packages</heading>
799 The Debian GNU/Linux distribution is based on the Debian
800 package management system, called <prgn>dpkg</prgn>. Thus,
801 all packages in the Debian distribution must be provided
802 in the <tt>.deb</tt> file format.
806 A <tt>.deb</tt> package contains two sets of files: a set of files
807 to install on the system when the package is installed, and a set
808 of files that provide additional metadata about the package or
809 which are executed when the package is installed or removed. This
810 second set of files is called <em>control information files</em>.
811 Among those files are the package maintainer scripts
812 and <file>control</file>, the <qref id="binarycontrolfiles">binary
813 package control file</qref> that contains the control fields for
814 the package. Other control information files
815 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
816 file</qref> used to store shared library dependency information
817 and the <file>conffiles</file> file that lists the package's
818 configuration files (described in <ref id="config-files">).
822 There is unfortunately a collision of terminology here between
823 control information files and files in the Debian control file
824 format. Throughout this document, a <em>control file</em> refers
825 to a file in the Debian control file format. These files are
826 documented in <ref id="controlfields">. Only files referred to
827 specifically as <em>control information files</em> are the files
828 included in the control information file member of
829 the <file>.deb</file> file format used by binary packages. Most
830 control information files are not in the Debian control file
835 <heading>The package name</heading>
838 Every package must have a name that's unique within the Debian
843 The package name is included in the control field
844 <tt>Package</tt>, the format of which is described
845 in <ref id="f-Package">.
846 The package name is also included as a part of the file name
847 of the <tt>.deb</tt> file.
852 <heading>The version of a package</heading>
855 Every package has a version number recorded in its
856 <tt>Version</tt> control file field, described in
857 <ref id="f-Version">.
861 The package management system imposes an ordering on version
862 numbers, so that it can tell whether packages are being up- or
863 downgraded and so that package system front end applications
864 can tell whether a package it finds available is newer than
865 the one installed on the system. The version number format
866 has the most significant parts (as far as comparison is
867 concerned) at the beginning.
871 If an upstream package has problematic version numbers they
872 should be converted to a sane form for use in the
873 <tt>Version</tt> field.
877 <heading>Version numbers based on dates</heading>
880 In general, Debian packages should use the same version
881 numbers as the upstream sources. However, upstream version
882 numbers based on some date formats (sometimes used for
883 development or "snapshot" releases) will not be ordered
884 correctly by the package management software. For
885 example, <prgn>dpkg</prgn> will consider "96May01" to be
886 greater than "96Dec24".
890 To prevent having to use epochs for every new upstream
891 version, the date-based portion of any upstream version number
892 should be given in a way that sorts correctly: four-digit year
893 first, followed by a two-digit numeric month, followed by a
894 two-digit numeric date, possibly with punctuation between the
899 Native Debian packages (i.e., packages which have been written
900 especially for Debian) whose version numbers include dates
901 should also follow these rules. If punctuation is desired
902 between the date components, remember that hyphen (<tt>-</tt>)
903 cannot be used in native package versions. Period
904 (<tt>.</tt>) is normally a good choice.
911 <heading>The maintainer of a package</heading>
914 Every package must have a Debian maintainer (the
915 maintainer may be one person or a group of people
916 reachable from a common email address, such as a mailing
917 list). The maintainer is responsible for ensuring that
918 the package is placed in the appropriate distributions.
922 The maintainer must be specified in the
923 <tt>Maintainer</tt> control field with their correct name
924 and a working email address. If one person maintains
925 several packages, they should try to avoid having
926 different forms of their name and email address in
927 the <tt>Maintainer</tt> fields of those packages.
931 The format of the <tt>Maintainer</tt> control field is
932 described in <ref id="f-Maintainer">.
936 If the maintainer of a package quits from the Debian
937 project, "Debian QA Group"
938 <email>packages@qa.debian.org</email> takes over the
939 maintainer-ship of the package until someone else
940 volunteers for that task. These packages are called
941 <em>orphaned packages</em>.<footnote>
942 The detailed procedure for doing this gracefully can
943 be found in the Debian Developer's Reference,
944 see <ref id="related">.
949 <sect id="descriptions">
950 <heading>The description of a package</heading>
953 Every Debian package must have a <tt>Description</tt> control
954 field which contains a synopsis and extended description of the
955 package. Technical information about the format of the
956 <tt>Description</tt> field is in <ref id="f-Description">.
960 The description should describe the package (the program) to a
961 user (system administrator) who has never met it before so that
962 they have enough information to decide whether they want to
963 install it. This description should not just be copied verbatim
964 from the program's documentation.
968 Put important information first, both in the synopsis and
969 extended description. Sometimes only the first part of the
970 synopsis or of the description will be displayed. You can
971 assume that there will usually be a way to see the whole
972 extended description.
976 The description should also give information about the
977 significant dependencies and conflicts between this package
978 and others, so that the user knows why these dependencies and
979 conflicts have been declared.
983 Instructions for configuring or using the package should
984 not be included (that is what installation scripts,
985 manual pages, info files, etc., are for). Copyright
986 statements and other administrivia should not be included
987 either (that is what the copyright file is for).
990 <sect1 id="synopsis"><heading>The single line synopsis</heading>
993 The single line synopsis should be kept brief - certainly
998 Do not include the package name in the synopsis line. The
999 display software knows how to display this already, and you
1000 do not need to state it. Remember that in many situations
1001 the user may only see the synopsis line - make it as
1002 informative as you can.
1007 <sect1 id="extendeddesc"><heading>The extended description</heading>
1010 Do not try to continue the single line synopsis into the
1011 extended description. This will not work correctly when
1012 the full description is displayed, and makes no sense
1013 where only the summary (the single line synopsis) is
1018 The extended description should describe what the package
1019 does and how it relates to the rest of the system (in terms
1020 of, for example, which subsystem it is which part of).
1024 The description field needs to make sense to anyone, even
1025 people who have no idea about any of the things the
1026 package deals with.<footnote>
1027 The blurb that comes with a program in its
1028 announcements and/or <prgn>README</prgn> files is
1029 rarely suitable for use in a description. It is
1030 usually aimed at people who are already in the
1031 community where the package is used.
1040 <heading>Dependencies</heading>
1043 Every package must specify the dependency information
1044 about other packages that are required for the first to
1049 For example, a dependency entry must be provided for any
1050 shared libraries required by a dynamically-linked executable
1051 binary in a package.
1055 Packages are not required to declare any dependencies they
1056 have on other packages which are marked <tt>Essential</tt>
1057 (see below), and should not do so unless they depend on a
1058 particular version of that package.<footnote>
1060 Essential is needed in part to avoid unresolvable dependency
1061 loops on upgrade. If packages add unnecessary dependencies
1062 on packages in this set, the chances that there
1063 <strong>will</strong> be an unresolvable dependency loop
1064 caused by forcing these Essential packages to be configured
1065 first before they need to be is greatly increased. It also
1066 increases the chances that frontends will be unable to
1067 <strong>calculate</strong> an upgrade path, even if one
1071 Also, functionality is rarely ever removed from the
1072 Essential set, but <em>packages</em> have been removed from
1073 the Essential set when the functionality moved to a
1074 different package. So depending on these packages <em>just
1075 in case</em> they stop being essential does way more harm
1082 Sometimes, a package requires another package to be installed
1083 <em>and</em> configured before it can be installed. In this
1084 case, you must specify a <tt>Pre-Depends</tt> entry for
1089 You should not specify a <tt>Pre-Depends</tt> entry for a
1090 package before this has been discussed on the
1091 <tt>debian-devel</tt> mailing list and a consensus about
1092 doing that has been reached.
1096 The format of the package interrelationship control fields is
1097 described in <ref id="relationships">.
1101 <sect id="virtual_pkg">
1102 <heading>Virtual packages</heading>
1105 Sometimes, there are several packages which offer
1106 more-or-less the same functionality. In this case, it's
1107 useful to define a <em>virtual package</em> whose name
1108 describes that common functionality. (The virtual
1109 packages only exist logically, not physically; that's why
1110 they are called <em>virtual</em>.) The packages with this
1111 particular function will then <em>provide</em> the virtual
1112 package. Thus, any other package requiring that function
1113 can simply depend on the virtual package without having to
1114 specify all possible packages individually.
1118 All packages should use virtual package names where
1119 appropriate, and arrange to create new ones if necessary.
1120 They should not use virtual package names (except privately,
1121 amongst a cooperating group of packages) unless they have
1122 been agreed upon and appear in the list of virtual package
1123 names. (See also <ref id="virtual">)
1127 The latest version of the authoritative list of virtual
1128 package names can be found in the <tt>debian-policy</tt> package.
1129 It is also available from the Debian web mirrors at
1130 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1131 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1135 The procedure for updating the list is described in the preface
1142 <heading>Base system</heading>
1145 The <tt>base system</tt> is a minimum subset of the Debian
1146 GNU/Linux system that is installed before everything else
1147 on a new system. Only very few packages are allowed to form
1148 part of the base system, in order to keep the required disk
1153 The base system consists of all those packages with priority
1154 <tt>required</tt> or <tt>important</tt>. Many of them will
1155 be tagged <tt>essential</tt> (see below).
1160 <heading>Essential packages</heading>
1163 Essential is defined as the minimal set of functionality that
1164 must be available and usable on the system at all times, even
1165 when packages are in an unconfigured (but unpacked) state.
1166 Packages are tagged <tt>essential</tt> for a system using the
1167 <tt>Essential</tt> control field. The format of the
1168 <tt>Essential</tt> control field is described in <ref
1173 Since these packages cannot be easily removed (one has to
1174 specify an extra <em>force option</em> to
1175 <prgn>dpkg</prgn> to do so), this flag must not be used
1176 unless absolutely necessary. A shared library package
1177 must not be tagged <tt>essential</tt>; dependencies will
1178 prevent its premature removal, and we need to be able to
1179 remove it when it has been superseded.
1183 Since dpkg will not prevent upgrading of other packages
1184 while an <tt>essential</tt> package is in an unconfigured
1185 state, all <tt>essential</tt> packages must supply all of
1186 their core functionality even when unconfigured. If the
1187 package cannot satisfy this requirement it must not be
1188 tagged as essential, and any packages depending on this
1189 package must instead have explicit dependency fields as
1194 Maintainers should take great care in adding any programs,
1195 interfaces, or functionality to <tt>essential</tt> packages.
1196 Packages may assume that functionality provided by
1197 <tt>essential</tt> packages is always available without
1198 declaring explicit dependencies, which means that removing
1199 functionality from the Essential set is very difficult and is
1200 almost never done. Any capability added to an
1201 <tt>essential</tt> package therefore creates an obligation to
1202 support that capability as part of the Essential set in
1207 You must not tag any packages <tt>essential</tt> before
1208 this has been discussed on the <tt>debian-devel</tt>
1209 mailing list and a consensus about doing that has been
1214 <sect id="maintscripts">
1215 <heading>Maintainer Scripts</heading>
1218 The package installation scripts should avoid producing
1219 output which is unnecessary for the user to see and
1220 should rely on <prgn>dpkg</prgn> to stave off boredom on
1221 the part of a user installing many packages. This means,
1222 amongst other things, using the <tt>--quiet</tt> option on
1223 <prgn>install-info</prgn>.
1227 Errors which occur during the execution of an installation
1228 script must be checked and the installation must not
1229 continue after an error.
1233 Note that in general <ref id="scripts"> applies to package
1234 maintainer scripts, too.
1238 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1239 to another package without consulting the maintainer of that
1240 package first. When adding or removing diversions, package
1241 maintainer scripts must provide the <tt>--package</tt> flag
1242 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1246 All packages which supply an instance of a common command
1247 name (or, in general, filename) should generally use
1248 <prgn>update-alternatives</prgn>, so that they may be
1249 installed together. If <prgn>update-alternatives</prgn>
1250 is not used, then each package must use
1251 <tt>Conflicts</tt> to ensure that other packages are
1252 de-installed. (In this case, it may be appropriate to
1253 specify a conflict against earlier versions of something
1254 that previously did not use
1255 <prgn>update-alternatives</prgn>; this is an exception to
1256 the usual rule that versioned conflicts should be
1260 <sect1 id="maintscriptprompt">
1261 <heading>Prompting in maintainer scripts</heading>
1263 Package maintainer scripts may prompt the user if
1264 necessary. Prompting must be done by communicating
1265 through a program, such as <prgn>debconf</prgn>, which
1266 conforms to the Debian Configuration Management
1267 Specification, version 2 or higher.
1271 Packages which are essential, or which are dependencies of
1272 essential packages, may fall back on another prompting method
1273 if no such interface is available when they are executed.
1277 The Debian Configuration Management Specification is included
1278 in the <file>debconf_specification</file> files in the
1279 <package>debian-policy</package> package.
1280 It is also available from the Debian web mirrors at
1281 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1282 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1286 Packages which use the Debian Configuration Management
1287 Specification may contain the additional control information
1288 files <file>config</file>
1289 and <file>templates</file>. <file>config</file> is an
1290 additional maintainer script used for package configuration,
1291 and <file>templates</file> contains templates used for user
1292 prompting. The <prgn>config</prgn> script might be run before
1293 the <prgn>preinst</prgn> script and before the package is
1294 unpacked or any of its dependencies or pre-dependencies are
1295 satisfied. Therefore it must work using only the tools
1296 present in <em>essential</em> packages.<footnote>
1297 <package>Debconf</package> or another tool that
1298 implements the Debian Configuration Management
1299 Specification will also be installed, and any
1300 versioned dependencies on it will be satisfied
1301 before preconfiguration begins.
1306 Packages which use the Debian Configuration Management
1307 Specification must allow for translation of their user-visible
1308 messages by using a gettext-based system such as the one
1309 provided by the <package>po-debconf</package> package.
1313 Packages should try to minimize the amount of prompting
1314 they need to do, and they should ensure that the user
1315 will only ever be asked each question once. This means
1316 that packages should try to use appropriate shared
1317 configuration files (such as <file>/etc/papersize</file> and
1318 <file>/etc/news/server</file>), and shared
1319 <package>debconf</package> variables rather than each
1320 prompting for their own list of required pieces of
1325 It also means that an upgrade should not ask the same
1326 questions again, unless the user has used
1327 <tt>dpkg --purge</tt> to remove the package's configuration.
1328 The answers to configuration questions should be stored in an
1329 appropriate place in <file>/etc</file> so that the user can
1330 modify them, and how this has been done should be
1335 If a package has a vitally important piece of
1336 information to pass to the user (such as "don't run me
1337 as I am, you must edit the following configuration files
1338 first or you risk your system emitting badly-formatted
1339 messages"), it should display this in the
1340 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1341 prompt the user to hit return to acknowledge the
1342 message. Copyright messages do not count as vitally
1343 important (they belong in
1344 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1345 neither do instructions on how to use a program (these
1346 should be in on-line documentation, where all the users
1351 Any necessary prompting should almost always be confined
1352 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1353 script. If it is done in the <prgn>postinst</prgn>, it
1354 should be protected with a conditional so that
1355 unnecessary prompting doesn't happen if a package's
1356 installation fails and the <prgn>postinst</prgn> is
1357 called with <tt>abort-upgrade</tt>,
1358 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1368 <heading>Source packages</heading>
1370 <sect id="standardsversion">
1371 <heading>Standards conformance</heading>
1374 Source packages should specify the most recent version number
1375 of this policy document with which your package complied
1376 when it was last updated.
1380 This information may be used to file bug reports
1381 automatically if your package becomes too much out of date.
1385 The version is specified in the <tt>Standards-Version</tt>
1387 The format of the <tt>Standards-Version</tt> field is
1388 described in <ref id="f-Standards-Version">.
1392 You should regularly, and especially if your package has
1393 become out of date, check for the newest Policy Manual
1394 available and update your package, if necessary. When your
1395 package complies with the new standards you should update the
1396 <tt>Standards-Version</tt> source package field and
1397 release it.<footnote>
1398 See the file <file>upgrading-checklist</file> for
1399 information about policy which has changed between
1400 different versions of this document.
1406 <sect id="pkg-relations">
1407 <heading>Package relationships</heading>
1410 Source packages should specify which binary packages they
1411 require to be installed or not to be installed in order to
1412 build correctly. For example, if building a package
1413 requires a certain compiler, then the compiler should be
1414 specified as a build-time dependency.
1418 It is not necessary to explicitly specify build-time
1419 relationships on a minimal set of packages that are always
1420 needed to compile, link and put in a Debian package a
1421 standard "Hello World!" program written in C or C++. The
1422 required packages are called <em>build-essential</em>, and
1423 an informational list can be found in
1424 <file>/usr/share/doc/build-essential/list</file> (which is
1425 contained in the <tt>build-essential</tt>
1428 <list compact="compact">
1430 This allows maintaining the list separately
1431 from the policy documents (the list does not
1432 need the kind of control that the policy
1436 Having a separate package allows one to install
1437 the build-essential packages on a machine, as
1438 well as allowing other packages such as tasks to
1439 require installation of the build-essential
1440 packages using the depends relation.
1443 The separate package allows bug reports against
1444 the list to be categorized separately from
1445 the policy management process in the BTS.
1452 When specifying the set of build-time dependencies, one
1453 should list only those packages explicitly required by the
1454 build. It is not necessary to list packages which are
1455 required merely because some other package in the list of
1456 build-time dependencies depends on them.<footnote>
1457 The reason for this is that dependencies change, and
1458 you should list all those packages, and <em>only</em>
1459 those packages that <em>you</em> need directly. What
1460 others need is their business. For example, if you
1461 only link against <file>libimlib</file>, you will need to
1462 build-depend on <package>libimlib2-dev</package> but
1463 not against any <tt>libjpeg*</tt> packages, even
1464 though <tt>libimlib2-dev</tt> currently depends on
1465 them: installation of <package>libimlib2-dev</package>
1466 will automatically ensure that all of its run-time
1467 dependencies are satisfied.
1472 If build-time dependencies are specified, it must be
1473 possible to build the package and produce working binaries
1474 on a system with only essential and build-essential
1475 packages installed and also those required to satisfy the
1476 build-time relationships (including any implied
1477 relationships). In particular, this means that version
1478 clauses should be used rigorously in build-time
1479 relationships so that one cannot produce bad or
1480 inconsistently configured packages when the relationships
1481 are properly satisfied.
1485 <ref id="relationships"> explains the technical details.
1490 <heading>Changes to the upstream sources</heading>
1493 If changes to the source code are made that are not
1494 specific to the needs of the Debian system, they should be
1495 sent to the upstream authors in whatever form they prefer
1496 so as to be included in the upstream version of the
1501 If you need to configure the package differently for
1502 Debian or for Linux, and the upstream source doesn't
1503 provide a way to do so, you should add such configuration
1504 facilities (for example, a new <prgn>autoconf</prgn> test
1505 or <tt>#define</tt>) and send the patch to the upstream
1506 authors, with the default set to the way they originally
1507 had it. You can then easily override the default in your
1508 <file>debian/rules</file> or wherever is appropriate.
1512 You should make sure that the <prgn>configure</prgn> utility
1513 detects the correct architecture specification string
1514 (refer to <ref id="arch-spec"> for details).
1518 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1519 <prgn>configure</prgn> scripts are used, you should edit the
1520 <file>.in</file> files rather than editing the
1521 <prgn>Makefile</prgn> directly. This allows the user to
1522 reconfigure the package if necessary. You should
1523 <em>not</em> configure the package and edit the generated
1524 <prgn>Makefile</prgn>! This makes it impossible for someone
1525 else to later reconfigure the package without losing the
1531 <sect id="dpkgchangelog">
1532 <heading>Debian changelog: <file>debian/changelog</file></heading>
1535 Changes in the Debian version of the package should be
1536 briefly explained in the Debian changelog file
1537 <file>debian/changelog</file>.<footnote>
1539 Mistakes in changelogs are usually best rectified by
1540 making a new changelog entry rather than "rewriting
1541 history" by editing old changelog entries.
1544 This includes modifications
1545 made in the Debian package compared to the upstream one
1546 as well as other changes and updates to the package.
1548 Although there is nothing stopping an author who is also
1549 the Debian maintainer from using this changelog for all
1550 their changes, it will have to be renamed if the Debian
1551 and upstream maintainers become different people. In such
1552 a case, however, it might be better to maintain the package
1553 as a non-native package.
1558 The format of the <file>debian/changelog</file> allows the
1559 package building tools to discover which version of the package
1560 is being built and find out other release-specific information.
1564 That format is a series of entries like this:
1566 <example compact="compact">
1567 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1569 [optional blank line(s), stripped]
1571 * <var>change details</var>
1572 <var>more change details</var>
1574 [blank line(s), included in output of dpkg-parsechangelog]
1576 * <var>even more change details</var>
1578 [optional blank line(s), stripped]
1580 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1585 <var>package</var> and <var>version</var> are the source
1586 package name and version number.
1590 <var>distribution(s)</var> lists the distributions where
1591 this version should be installed when it is uploaded - it
1592 is copied to the <tt>Distribution</tt> field in the
1593 <file>.changes</file> file. See <ref id="f-Distribution">.
1597 <var>urgency</var> is the value for the <tt>Urgency</tt>
1598 field in the <file>.changes</file> file for the upload
1599 (see <ref id="f-Urgency">). It is not possible to specify
1600 an urgency containing commas; commas are used to separate
1601 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1602 <prgn>dpkg</prgn> changelog format (though there is
1603 currently only one useful <var>keyword</var>,
1608 The change details may in fact be any series of lines
1609 starting with at least two spaces, but conventionally each
1610 change starts with an asterisk and a separating space and
1611 continuation lines are indented so as to bring them in
1612 line with the start of the text above. Blank lines may be
1613 used here to separate groups of changes, if desired.
1617 If this upload resolves bugs recorded in the Bug Tracking
1618 System (BTS), they may be automatically closed on the
1619 inclusion of this package into the Debian archive by
1620 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1621 in the change details.<footnote>
1622 To be precise, the string should match the following
1623 Perl regular expression:
1625 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1627 Then all of the bug numbers listed will be closed by the
1628 archive maintenance script (<prgn>katie</prgn>) using the
1629 <var>version</var> of the changelog entry.
1631 This information is conveyed via the <tt>Closes</tt> field
1632 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1636 The maintainer name and email address used in the changelog
1637 should be the details of the person uploading <em>this</em>
1638 version. They are <em>not</em> necessarily those of the
1639 usual package maintainer<footnote>
1640 If the developer uploading the package is not one of the usual
1641 maintainers of the package (as listed in the
1642 <qref id="f-Maintainer"><tt>Maintainer</tt></qref> or
1643 <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control fields of
1644 the package), the first line of the changelog is conventionally used
1645 to explain why a non-maintainer is uploading the package. The
1646 Debian Developer's Reference (see <ref id="related">) documents the
1647 conventions used.</footnote>. The information here will be
1648 copied to the <tt>Changed-By</tt> field in the
1649 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1650 and then later used to send an acknowledgement when the
1651 upload has been installed.
1655 The <var>date</var> has the following format<footnote>
1656 This is the same as the format generated by <tt>date
1658 </footnote> (compatible and with the same semantics of
1659 RFC 2822 and RFC 5322):
1660 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1662 <list compact="compact">
1664 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1667 dd is a one- or two-digit day of the month (01-31)
1670 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1673 <item>yyyy is the four-digit year (e.g. 2010)</item>
1674 <item>hh is the two-digit hour (00-23)</item>
1675 <item>mm is the two-digit minutes (00-59)</item>
1676 <item>ss is the two-digit seconds (00-60)</item>
1678 +zzzz or -zzzz is the the time zone offset from Coordinated
1679 Universal Time (UTC). "+" indicates that the time is ahead
1680 of (i.e., east of) UTC and "-" indicates that the time is
1681 behind (i.e., west of) UTC. The first two digits indicate
1682 the hour difference from UTC and the last two digits
1683 indicate the number of additional minutes difference from
1684 UTC. The last two digits must be in the range 00-59.
1690 The first "title" line with the package name must start
1691 at the left hand margin. The "trailer" line with the
1692 maintainer and date details must be preceded by exactly
1693 one space. The maintainer details and the date must be
1694 separated by exactly two spaces.
1698 The entire changelog must be encoded in UTF-8.
1702 For more information on placement of the changelog files
1703 within binary packages, please see <ref id="changelogs">.
1707 <sect id="dpkgcopyright">
1708 <heading>Copyright: <file>debian/copyright</file></heading>
1710 Every package must be accompanied by a verbatim copy of its
1711 copyright information and distribution license in the file
1712 <file>/usr/share/doc/<var>package</var>/copyright</file>
1713 (see <ref id="copyrightfile"> for further details). Also see
1714 <ref id="pkgcopyright"> for further considerations related
1715 to copyrights for packages.
1719 <heading>Error trapping in makefiles</heading>
1722 When <prgn>make</prgn> invokes a command in a makefile
1723 (including your package's upstream makefiles and
1724 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1725 means that <prgn>sh</prgn>'s usual bad error handling
1726 properties apply: if you include a miniature script as one
1727 of the commands in your makefile you'll find that if you
1728 don't do anything about it then errors are not detected
1729 and <prgn>make</prgn> will blithely continue after
1734 Every time you put more than one shell command (this
1735 includes using a loop) in a makefile command you
1736 must make sure that errors are trapped. For
1737 simple compound commands, such as changing directory and
1738 then running a program, using <tt>&&</tt> rather
1739 than semicolon as a command separator is sufficient. For
1740 more complex commands including most loops and
1741 conditionals you should include a separate <tt>set -e</tt>
1742 command at the start of every makefile command that's
1743 actually one of these miniature shell scripts.
1747 <sect id="timestamps">
1748 <heading>Time Stamps</heading>
1750 Maintainers should preserve the modification times of the
1751 upstream source files in a package, as far as is reasonably
1753 The rationale is that there is some information conveyed
1754 by knowing the age of the file, for example, you could
1755 recognize that some documentation is very old by looking
1756 at the modification time, so it would be nice if the
1757 modification time of the upstream source would be
1763 <sect id="restrictions">
1764 <heading>Restrictions on objects in source packages</heading>
1767 The source package may not contain any hard links<footnote>
1769 This is not currently detected when building source
1770 packages, but only when extracting
1774 Hard links may be permitted at some point in the
1775 future, but would require a fair amount of
1778 </footnote>, device special files, sockets or setuid or
1779 setgid files.<footnote>
1780 Setgid directories are allowed.
1785 <sect id="debianrules">
1786 <heading>Main building script: <file>debian/rules</file></heading>
1789 This file must be an executable makefile, and contains the
1790 package-specific recipes for compiling the package and
1791 building binary package(s) from the source.
1795 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1796 so that it can be invoked by saying its name rather than
1797 invoking <prgn>make</prgn> explicitly. That is, invoking
1798 either of <tt>make -f debian/rules <em>args...</em></tt>
1799 or <tt>./debian/rules <em>args...</em></tt> must result in
1804 Since an interactive <file>debian/rules</file> script makes it
1805 impossible to auto-compile that package and also makes it
1806 hard for other people to reproduce the same binary
1807 package, all <em>required targets</em> must be
1808 non-interactive. At a minimum, required targets are the
1809 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1810 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1811 <em>binary-indep</em>, and <em>build</em>. It also follows
1812 that any target that these targets depend on must also be
1817 The targets are as follows (required unless stated otherwise):
1819 <tag><tt>build</tt></tag>
1822 The <tt>build</tt> target should perform all the
1823 configuration and compilation of the package.
1824 If a package has an interactive pre-build
1825 configuration routine, the Debian source package
1826 must either be built after this has taken place (so
1827 that the binary package can be built without rerunning
1828 the configuration) or the configuration routine
1829 modified to become non-interactive. (The latter is
1830 preferable if there are architecture-specific features
1831 detected by the configuration routine.)
1835 For some packages, notably ones where the same
1836 source tree is compiled in different ways to produce
1837 two binary packages, the <tt>build</tt> target
1838 does not make much sense. For these packages it is
1839 good enough to provide two (or more) targets
1840 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1841 for each of the ways of building the package, and a
1842 <tt>build</tt> target that does nothing. The
1843 <tt>binary</tt> target will have to build the
1844 package in each of the possible ways and make the
1845 binary package out of each.
1849 The <tt>build</tt> target must not do anything
1850 that might require root privilege.
1854 The <tt>build</tt> target may need to run the
1855 <tt>clean</tt> target first - see below.
1859 When a package has a configuration and build routine
1860 which takes a long time, or when the makefiles are
1861 poorly designed, or when <tt>build</tt> needs to
1862 run <tt>clean</tt> first, it is a good idea to
1863 <tt>touch build</tt> when the build process is
1864 complete. This will ensure that if <tt>debian/rules
1865 build</tt> is run again it will not rebuild the whole
1867 Another common way to do this is for <tt>build</tt>
1868 to depend on <prgn>build-stamp</prgn> and to do
1869 nothing else, and for the <prgn>build-stamp</prgn>
1870 target to do the building and to <tt>touch
1871 build-stamp</tt> on completion. This is
1872 especially useful if the build routine creates a
1873 file or directory called <tt>build</tt>; in such a
1874 case, <tt>build</tt> will need to be listed as
1875 a phony target (i.e., as a dependency of the
1876 <tt>.PHONY</tt> target). See the documentation of
1877 <prgn>make</prgn> for more information on phony
1883 <tag><tt>build-arch</tt> (optional),
1884 <tt>build-indep</tt> (optional)
1888 A package may also provide both of the targets
1889 <tt>build-arch</tt> and <tt>build-indep</tt>.
1890 The <tt>build-arch</tt> target, if provided, should
1891 perform all the configuration and compilation required for
1892 producing all architecture-dependant binary packages
1893 (those packages for which the body of the
1894 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1895 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1896 target, if provided, should perform all the configuration
1897 and compilation required for producing all
1898 architecture-independent binary packages (those packages
1899 for which the body of the <tt>Architecture</tt> field
1900 in <tt>debian/control</tt> is <tt>all</tt>).
1901 The <tt>build</tt> target should depend on those of the
1902 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1903 are provided in the rules file.<footnote>
1904 The intent of this split is so that binary-only builds
1905 need not install the dependencies required for
1906 the <tt>build-indep</tt> target. However, this is not
1907 yet used in practice since <tt>dpkg-buildpackage
1908 -B</tt>, and therefore the autobuilders,
1909 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1910 due to the difficulties in determining whether the
1911 optional <tt>build-arch</tt> target exists.
1916 If one or both of the targets <tt>build-arch</tt> and
1917 <tt>build-indep</tt> are not provided, then invoking
1918 <file>debian/rules</file> with one of the not-provided
1919 targets as arguments should produce a exit status code
1920 of 2. Usually this is provided automatically by make
1921 if the target is missing.
1925 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1926 must not do anything that might require root privilege.
1930 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1931 <tt>binary-indep</tt>
1935 The <tt>binary</tt> target must be all that is
1936 necessary for the user to build the binary package(s)
1937 produced from this source package. It is
1938 split into two parts: <prgn>binary-arch</prgn> builds
1939 the binary packages which are specific to a particular
1940 architecture, and <tt>binary-indep</tt> builds
1941 those which are not.
1944 <tt>binary</tt> may be (and commonly is) a target with
1945 no commands which simply depends on
1946 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1949 Both <tt>binary-*</tt> targets should depend on the
1950 <tt>build</tt> target, or on the appropriate
1951 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1952 provided, so that the package is built if it has not
1953 been already. It should then create the relevant
1954 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1955 make their control files and <prgn>dpkg-deb</prgn> to
1956 build them and place them in the parent of the top
1961 Both the <tt>binary-arch</tt> and
1962 <tt>binary-indep</tt> targets <em>must</em> exist.
1963 If one of them has nothing to do (which will always be
1964 the case if the source generates only a single binary
1965 package, whether architecture-dependent or not), it
1966 must still exist and must always succeed.
1970 The <tt>binary</tt> targets must be invoked as
1972 The <prgn>fakeroot</prgn> package often allows one
1973 to build a package correctly even without being
1979 <tag><tt>clean</tt></tag>
1982 This must undo any effects that the <tt>build</tt>
1983 and <tt>binary</tt> targets may have had, except
1984 that it should leave alone any output files created in
1985 the parent directory by a run of a <tt>binary</tt>
1990 If a <tt>build</tt> file is touched at the end of
1991 the <tt>build</tt> target, as suggested above, it
1992 should be removed as the first action that
1993 <tt>clean</tt> performs, so that running
1994 <tt>build</tt> again after an interrupted
1995 <tt>clean</tt> doesn't think that everything is
2000 The <tt>clean</tt> target may need to be
2001 invoked as root if <tt>binary</tt> has been
2002 invoked since the last <tt>clean</tt>, or if
2003 <tt>build</tt> has been invoked as root (since
2004 <tt>build</tt> may create directories, for
2009 <tag><tt>get-orig-source</tt> (optional)</tag>
2012 This target fetches the most recent version of the
2013 original source package from a canonical archive site
2014 (via FTP or WWW, for example), does any necessary
2015 rearrangement to turn it into the original source
2016 tar file format described below, and leaves it in the
2021 This target may be invoked in any directory, and
2022 should take care to clean up any temporary files it
2027 This target is optional, but providing it if
2028 possible is a good idea.
2032 <tag><tt>patch</tt> (optional)</tag>
2035 This target performs whatever additional actions are
2036 required to make the source ready for editing (unpacking
2037 additional upstream archives, applying patches, etc.).
2038 It is recommended to be implemented for any package where
2039 <tt>dpkg-source -x</tt> does not result in source ready
2040 for additional modification. See
2041 <ref id="readmesource">.
2047 The <tt>build</tt>, <tt>binary</tt> and
2048 <tt>clean</tt> targets must be invoked with the current
2049 directory being the package's top-level directory.
2054 Additional targets may exist in <file>debian/rules</file>,
2055 either as published or undocumented interfaces or for the
2056 package's internal use.
2060 The architectures we build on and build for are determined
2061 by <prgn>make</prgn> variables using the utility
2062 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2063 You can determine the
2064 Debian architecture and the GNU style architecture
2065 specification string for the build machine (the machine type
2066 we are building on) as well as for the host machine (the
2067 machine type we are building for). Here is a list of
2068 supported <prgn>make</prgn> variables:
2069 <list compact="compact">
2071 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2074 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2077 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2080 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2081 specification string)
2084 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2085 <tt>DEB_*_GNU_TYPE</tt>)
2088 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2089 <tt>DEB_*_GNU_TYPE</tt>)
2091 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2092 the build machine or <tt>HOST</tt> for specification of the
2097 Backward compatibility can be provided in the rules file
2098 by setting the needed variables to suitable default
2099 values; please refer to the documentation of
2100 <prgn>dpkg-architecture</prgn> for details.
2104 It is important to understand that the <tt>DEB_*_ARCH</tt>
2105 string only determines which Debian architecture we are
2106 building on or for. It should not be used to get the CPU
2107 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2108 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2109 GNU style variables should generally only be used with upstream
2113 <sect1 id="debianrules-options">
2114 <heading><file>debian/rules</file> and
2115 <tt>DEB_BUILD_OPTIONS</tt></heading>
2118 Supporting the standardized environment variable
2119 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2120 contain several flags to change how a package is compiled and
2121 built. Each flag must be in the form <var>flag</var> or
2122 <var>flag</var>=<var>options</var>. If multiple flags are
2123 given, they must be separated by whitespace.<footnote>
2124 Some packages support any delimiter, but whitespace is the
2125 easiest to parse inside a makefile and avoids ambiguity with
2126 flag values that contain commas.
2128 <var>flag</var> must start with a lowercase letter
2129 (<tt>a-z</tt>) and consist only of lowercase letters,
2130 numbers (<tt>0-9</tt>), and the characters
2131 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2132 <var>options</var> must not contain whitespace. The same
2133 tag should not be given multiple times with conflicting
2134 values. Package maintainers may assume that
2135 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2139 The meaning of the following tags has been standardized:
2143 This tag says to not run any build-time test suite
2144 provided by the package.
2148 The presence of this tag means that the package should
2149 be compiled with a minimum of optimization. For C
2150 programs, it is best to add <tt>-O0</tt> to
2151 <tt>CFLAGS</tt> (although this is usually the default).
2152 Some programs might fail to build or run at this level
2153 of optimization; it may be necessary to use
2154 <tt>-O1</tt>, for example.
2158 This tag means that the debugging symbols should not be
2159 stripped from the binary during installation, so that
2160 debugging information may be included in the package.
2162 <tag>parallel=n</tag>
2164 This tag means that the package should be built using up
2165 to <tt>n</tt> parallel processes if the package build
2166 system supports this.<footnote>
2167 Packages built with <tt>make</tt> can often implement
2168 this by passing the <tt>-j</tt><var>n</var> option to
2171 If the package build system does not support parallel
2172 builds, this string must be ignored. If the package
2173 build system only supports a lower level of concurrency
2174 than <var>n</var>, the package should be built using as
2175 many parallel processes as the package build system
2176 supports. It is up to the package maintainer to decide
2177 whether the package build times are long enough and the
2178 package build system is robust enough to make supporting
2179 parallel builds worthwhile.
2185 Unknown flags must be ignored by <file>debian/rules</file>.
2189 The following makefile snippet is an example of how one may
2190 implement the build options; you will probably have to
2191 massage this example in order to make it work for your
2193 <example compact="compact">
2196 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2197 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2198 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2199 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2201 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2206 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2207 INSTALL_PROGRAM += -s
2209 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2210 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2211 MAKEFLAGS += -j$(NUMJOBS)
2216 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2217 # Code to run the package test suite.
2224 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2225 <sect id="substvars">
2226 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2229 When <prgn>dpkg-gencontrol</prgn>
2230 generates <qref id="binarycontrolfiles">binary package control
2231 files</qref> (<file>DEBIAN/control</file>), it performs variable
2232 substitutions on its output just before writing it. Variable
2233 substitutions have the form <tt>${<var>variable</var>}</tt>.
2234 The optional file <file>debian/substvars</file> contains
2235 variable substitutions to be used; variables can also be set
2236 directly from <file>debian/rules</file> using the <tt>-V</tt>
2237 option to the source packaging commands, and certain predefined
2238 variables are also available.
2242 The <file>debian/substvars</file> file is usually generated and
2243 modified dynamically by <file>debian/rules</file> targets, in
2244 which case it must be removed by the <tt>clean</tt> target.
2248 See <manref name="deb-substvars" section="5"> for full
2249 details about source variable substitutions, including the
2250 format of <file>debian/substvars</file>.</p>
2253 <sect id="debianwatch">
2254 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2257 This is an optional, recommended configuration file for the
2258 <tt>uscan</tt> utility which defines how to automatically scan
2259 ftp or http sites for newly available updates of the
2260 package. This is used
2261 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2262 tools to help with quality control and maintenance of the
2263 distribution as a whole.
2268 <sect id="debianfiles">
2269 <heading>Generated files list: <file>debian/files</file></heading>
2272 This file is not a permanent part of the source tree; it
2273 is used while building packages to record which files are
2274 being generated. <prgn>dpkg-genchanges</prgn> uses it
2275 when it generates a <file>.changes</file> file.
2279 It should not exist in a shipped source package, and so it
2280 (and any backup files or temporary files such as
2281 <file>files.new</file><footnote>
2282 <file>files.new</file> is used as a temporary file by
2283 <prgn>dpkg-gencontrol</prgn> and
2284 <prgn>dpkg-distaddfile</prgn> - they write a new
2285 version of <tt>files</tt> here before renaming it,
2286 to avoid leaving a corrupted copy if an error
2288 </footnote>) should be removed by the
2289 <tt>clean</tt> target. It may also be wise to
2290 ensure a fresh start by emptying or removing it at the
2291 start of the <tt>binary</tt> target.
2295 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2296 package, it adds an entry to <file>debian/files</file> for the
2297 <file>.deb</file> file that will be created when <tt>dpkg-deb
2298 --build</tt> is run for that binary package. So for most
2299 packages all that needs to be done with this file is to
2300 delete it in the <tt>clean</tt> target.
2304 If a package upload includes files besides the source
2305 package and any binary packages whose control files were
2306 made with <prgn>dpkg-gencontrol</prgn> then they should be
2307 placed in the parent of the package's top-level directory
2308 and <prgn>dpkg-distaddfile</prgn> should be called to add
2309 the file to the list in <file>debian/files</file>.</p>
2312 <sect id="embeddedfiles">
2313 <heading>Convenience copies of code</heading>
2316 Some software packages include in their distribution convenience
2317 copies of code from other software packages, generally so that
2318 users compiling from source don't have to download multiple
2319 packages. Debian packages should not make use of these
2320 convenience copies unless the included package is explicitly
2321 intended to be used in this way.<footnote>
2322 For example, parts of the GNU build system work like this.
2324 If the included code is already in the Debian archive in the
2325 form of a library, the Debian packaging should ensure that
2326 binary packages reference the libraries already in Debian and
2327 the convenience copy is not used. If the included code is not
2328 already in Debian, it should be packaged separately as a
2329 prerequisite if possible.
2331 Having multiple copies of the same code in Debian is
2332 inefficient, often creates either static linking or shared
2333 library conflicts, and, most importantly, increases the
2334 difficulty of handling security vulnerabilities in the
2340 <sect id="readmesource">
2341 <heading>Source package handling:
2342 <file>debian/README.source</file></heading>
2345 If running <prgn>dpkg-source -x</prgn> on a source package
2346 doesn't produce the source of the package, ready for editing,
2347 and allow one to make changes and run
2348 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2349 without taking any additional steps, creating a
2350 <file>debian/README.source</file> documentation file is
2351 recommended. This file should explain how to do all of the
2354 <item>Generate the fully patched source, in a form ready for
2355 editing, that would be built to create Debian
2356 packages. Doing this with a <tt>patch</tt> target in
2357 <file>debian/rules</file> is recommended; see
2358 <ref id="debianrules">.</item>
2359 <item>Modify the source and save those modifications so that
2360 they will be applied when building the package.</item>
2361 <item>Remove source modifications that are currently being
2362 applied when building the package.</item>
2363 <item>Optionally, document what steps are necessary to
2364 upgrade the Debian source package to a new upstream version,
2365 if applicable.</item>
2367 This explanation should include specific commands and mention
2368 any additional required Debian packages. It should not assume
2369 familiarity with any specific Debian packaging system or patch
2374 This explanation may refer to a documentation file installed by
2375 one of the package's build dependencies provided that the
2376 referenced documentation clearly explains these tasks and is not
2377 a general reference manual.
2381 <file>debian/README.source</file> may also include any other
2382 information that would be helpful to someone modifying the
2383 source package. Even if the package doesn't fit the above
2384 description, maintainers are encouraged to document in a
2385 <file>debian/README.source</file> file any source package with a
2386 particularly complex or unintuitive source layout or build
2387 system (for example, a package that builds the same source
2388 multiple times to generate different binary packages).
2394 <chapt id="controlfields">
2395 <heading>Control files and their fields</heading>
2398 The package management system manipulates data represented in
2399 a common format, known as <em>control data</em>, stored in
2400 <em>control files</em>.
2401 Control files are used for source packages, binary packages and
2402 the <file>.changes</file> files which control the installation
2403 of uploaded files<footnote>
2404 <prgn>dpkg</prgn>'s internal databases are in a similar
2409 <sect id="controlsyntax">
2410 <heading>Syntax of control files</heading>
2413 A control file consists of one or more paragraphs of
2415 The paragraphs are also sometimes referred to as stanzas.
2417 The paragraphs are separated by blank lines. Some control
2418 files allow only one paragraph; others allow several, in
2419 which case each paragraph usually refers to a different
2420 package. (For example, in source packages, the first
2421 paragraph refers to the source package, and later paragraphs
2422 refer to binary packages generated from the source.)
2426 Each paragraph consists of a series of data fields; each
2427 field consists of the field name, followed by a colon and
2428 then the data/value associated with that field. It ends at
2429 the end of the (logical) line. Horizontal whitespace
2430 (spaces and tabs) may occur immediately before or after the
2431 value and is ignored there; it is conventional to put a
2432 single space after the colon. For example, a field might
2434 <example compact="compact">
2437 the field name is <tt>Package</tt> and the field value
2442 A paragraph must not contain more than one instance of a
2443 particular field name.
2447 Many fields' values may span several lines; in this case
2448 each continuation line must start with a space or a tab.
2449 Any trailing spaces or tabs at the end of individual
2450 lines of a field value are ignored.
2454 In fields where it is specified that lines may not wrap,
2455 only a single line of data is allowed and whitespace is not
2456 significant in a field body. Whitespace must not appear
2457 inside names (of packages, architectures, files or anything
2458 else) or version numbers, or between the characters of
2459 multi-character version relationships.
2463 Field names are not case-sensitive, but it is usual to
2464 capitalize the field names using mixed case as shown below.
2465 Field values are case-sensitive unless the description of the
2466 field says otherwise.
2470 Blank lines, or lines consisting only of spaces and tabs,
2471 are not allowed within field values or between fields - that
2472 would mean a new paragraph.
2476 All control files must be encoded in UTF-8.
2480 <sect id="sourcecontrolfiles">
2481 <heading>Source package control files -- <file>debian/control</file></heading>
2484 The <file>debian/control</file> file contains the most vital
2485 (and version-independent) information about the source package
2486 and about the binary packages it creates.
2490 The first paragraph of the control file contains information about
2491 the source package in general. The subsequent sets each describe a
2492 binary package that the source tree builds.
2496 The fields in the general paragraph (the first one, for the source
2499 <list compact="compact">
2500 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2501 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2502 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2503 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2504 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2505 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2506 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2507 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2512 The fields in the binary package paragraphs are:
2514 <list compact="compact">
2515 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2516 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2517 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2518 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2519 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2520 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2521 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2522 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2527 The syntax and semantics of the fields are described below.
2531 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2532 generate control files for binary packages (see below), by
2533 <prgn>dpkg-genchanges</prgn> to generate the
2534 <file>.changes</file> file to accompany the upload, and by
2535 <prgn>dpkg-source</prgn> when it creates the
2536 <file>.dsc</file> source control file as part of a source
2537 archive. Many fields are permitted to span multiple lines in
2538 <file>debian/control</file> but not in any other control
2539 file. These tools are responsible for removing the line
2540 breaks from such fields when using fields from
2541 <file>debian/control</file> to generate other control files.
2545 The fields here may contain variable references - their
2546 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2547 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2548 when they generate output control files.
2549 See <ref id="substvars"> for details.
2553 In addition to the control file syntax described <qref
2554 id="controlsyntax">above</qref>, this file may also contain
2555 comment lines starting with <tt>#</tt> without any preceding
2556 whitespace. All such lines are ignored, even in the middle of
2557 continuation lines for a multiline field, and do not end a
2563 <sect id="binarycontrolfiles">
2564 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2567 The <file>DEBIAN/control</file> file contains the most vital
2568 (and version-dependent) information about a binary package. It
2569 consists of a single paragraph.
2573 The fields in this file are:
2575 <list compact="compact">
2576 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2577 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2578 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2579 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2580 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2581 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2582 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2583 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2584 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2585 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2586 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2587 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2592 <sect id="debiansourcecontrolfiles">
2593 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2596 This file consists of a single paragraph, possibly surrounded by
2597 a PGP signature. The fields of that paragraph are listed below.
2598 Their syntax is described above, in <ref id="pkg-controlfields">.
2600 <list compact="compact">
2601 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2602 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2603 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2604 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2605 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2606 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2607 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2608 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2609 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2610 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2611 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2612 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2613 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2618 The source package control file is generated by
2619 <prgn>dpkg-source</prgn> when it builds the source
2620 archive, from other files in the source package,
2621 described above. When unpacking, it is checked against
2622 the files and directories in the other parts of the
2628 <sect id="debianchangesfiles">
2629 <heading>Debian changes files -- <file>.changes</file></heading>
2632 The <file>.changes</file> files are used by the Debian archive
2633 maintenance software to process updates to packages. They
2634 consist of a single paragraph, possibly surrounded by a PGP
2635 signature. That paragraph contains information from the
2636 <file>debian/control</file> file and other data about the
2637 source package gathered via <file>debian/changelog</file>
2638 and <file>debian/rules</file>.
2642 <file>.changes</file> files have a format version that is
2643 incremented whenever the documented fields or their meaning
2644 change. This document describes format &changesversion;.
2648 The fields in this file are:
2650 <list compact="compact">
2651 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2652 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2653 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2654 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2655 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2656 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2657 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2658 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2659 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2660 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2661 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2662 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2663 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2664 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2665 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2666 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2671 <sect id="controlfieldslist">
2672 <heading>List of fields</heading>
2674 <sect1 id="f-Source">
2675 <heading><tt>Source</tt></heading>
2678 This field identifies the source package name.
2682 In <file>debian/control</file> or a <file>.dsc</file> file,
2683 this field must contain only the name of the source package.
2687 In a binary package control file or a <file>.changes</file>
2688 file, the source package name may be followed by a version
2689 number in parentheses<footnote>
2690 It is customary to leave a space after the package name
2691 if a version number is specified.
2693 This version number may be omitted (and is, by
2694 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2695 the <tt>Version</tt> field of the binary package in
2696 question. The field itself may be omitted from a binary
2697 package control file when the source package has the same
2698 name and version as the binary package.
2702 Package names (both source and binary,
2703 see <ref id="f-Package">) must consist only of lower case
2704 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2705 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2706 (<tt>.</tt>). They must be at least two characters long and
2707 must start with an alphanumeric character.
2711 <sect1 id="f-Maintainer">
2712 <heading><tt>Maintainer</tt></heading>
2715 The package maintainer's name and email address. The name
2716 must come first, then the email address inside angle
2717 brackets <tt><></tt> (in RFC822 format).
2721 If the maintainer's name contains a full stop then the
2722 whole field will not work directly as an email address due
2723 to a misfeature in the syntax specified in RFC822; a
2724 program using this field as an address must check for this
2725 and correct the problem if necessary (for example by
2726 putting the name in round brackets and moving it to the
2727 end, and bringing the email address forward).
2731 <sect1 id="f-Uploaders">
2732 <heading><tt>Uploaders</tt></heading>
2735 List of the names and email addresses of co-maintainers of
2736 the package, if any. If the package has other maintainers
2737 beside the one named in the
2738 <qref id="f-Maintainer">Maintainer field</qref>, their names
2739 and email addresses should be listed here. The format of each
2740 entry is the same as that of the Maintainer field, and
2741 multiple entries must be comma separated. This is an optional
2746 Any parser that interprets the Uploaders field in
2747 <file>debian/control</file> must permit it to span multiple
2748 lines. Line breaks in an Uploaders field that spans multiple
2749 lines are not significant and the semantics of the field are
2750 the same as if the line breaks had not been present.
2754 <sect1 id="f-Changed-By">
2755 <heading><tt>Changed-By</tt></heading>
2758 The name and email address of the person who prepared this
2759 version of the package, usually a maintainer. The syntax is
2760 the same as for the <qref id="f-Maintainer">Maintainer
2765 <sect1 id="f-Section">
2766 <heading><tt>Section</tt></heading>
2769 This field specifies an application area into which the package
2770 has been classified. See <ref id="subsections">.
2774 When it appears in the <file>debian/control</file> file,
2775 it gives the value for the subfield of the same name in
2776 the <tt>Files</tt> field of the <file>.changes</file> file.
2777 It also gives the default for the same field in the binary
2782 <sect1 id="f-Priority">
2783 <heading><tt>Priority</tt></heading>
2786 This field represents how important it is that the user
2787 have the package installed. See <ref id="priorities">.
2791 When it appears in the <file>debian/control</file> file,
2792 it gives the value for the subfield of the same name in
2793 the <tt>Files</tt> field of the <file>.changes</file> file.
2794 It also gives the default for the same field in the binary
2799 <sect1 id="f-Package">
2800 <heading><tt>Package</tt></heading>
2803 The name of the binary package.
2807 Binary package names must follow the same syntax and
2808 restrictions as source package names. See <ref id="f-Source">
2813 <sect1 id="f-Architecture">
2814 <heading><tt>Architecture</tt></heading>
2817 Depending on context and the control file used, the
2818 <tt>Architecture</tt> field can include the following sets of
2822 A unique single word identifying a Debian machine
2823 architecture as described in <ref id="arch-spec">.
2826 An architecture wildcard identifying a set of Debian
2827 machine architectures, see <ref id="arch-wildcard-spec">.
2828 <tt>any</tt> matches all Debian machine architectures
2829 and is the most frequently used.
2832 <tt>all</tt>, which indicates an
2833 architecture-independent package.
2836 <tt>source</tt>, which indicates a source package.
2842 In the main <file>debian/control</file> file in the source
2843 package, this field may contain the special
2844 value <tt>all</tt>, the special architecture
2845 wildcard <tt>any</tt>, or a list of specific and wildcard
2846 architectures separated by spaces. If <tt>all</tt>
2847 or <tt>any</tt> appears, that value must be the entire
2848 contents of the field. Most packages will use
2849 either <tt>all</tt> or <tt>any</tt>.
2853 Specifying a specific list of architectures indicates that the
2854 source will build an architecture-dependent package only on
2855 architectures included in the list. Specifying a list of
2856 architecture wildcards indicates that the source will build an
2857 architecture-dependent package on only those architectures
2858 that match any of the specified architecture wildcards.
2859 Specifying a list of architectures or architecture wildcards
2860 other than <tt>any</tt> is for the minority of cases where a
2861 program is not portable or is not useful on some
2862 architectures. Where possible, the program should be made
2867 In the source package control file <file>.dsc</file>, this
2868 field may contain either the architecture
2869 wildcard <tt>any</tt> or a list of architectures and
2870 architecture wildcards separated by spaces. If a list is
2871 given, it may include (or consist solely of) the special
2872 value <tt>all</tt>. In other words, in <file>.dsc</file>
2873 files unlike the <file>debian/control</file>, <tt>all</tt> may
2874 occur in combination with specific architectures.
2875 The <tt>Architecture</tt> field in the source package control
2876 file <file>.dsc</file> is generally constructed from
2877 the <tt>Architecture</tt> fields in
2878 the <file>debian/control</file> in the source package.
2882 Specifying <tt>any</tt> indicates that the source package
2883 isn't dependent on any particular architecture and should
2884 compile fine on any one. The produced binary package(s)
2885 will either be specific to whatever the current build
2886 architecture is or will be architecture-independent.
2890 Specifying only <tt>all</tt> indicates that the source package
2891 will only build architecture-independent packages. If this is
2892 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2893 <tt>any</tt> implies that the source package will build at
2894 least one architecture-dependent package.
2898 Specifying a list of architectures or architecture wildcards
2899 indicates that the source will build an architecture-dependent
2900 package, and will only work correctly on the listed or
2901 matching architectures. If the source package also builds at
2902 least one architecture-independent package, <tt>all</tt> will
2903 also be included in the list.
2907 In a <file>.changes</file> file, the <tt>Architecture</tt>
2908 field lists the architecture(s) of the package(s) currently
2909 being uploaded. This will be a list; if the source for the
2910 package is also being uploaded, the special
2911 entry <tt>source</tt> is also present. <tt>all</tt> will be
2912 present if any architecture-independent packages are being
2913 uploaded. Architecture wildcards such as <tt>any</tt> must
2914 never occur in the <tt>Architecture</tt> field in
2915 the <file>.changes</file> file.
2919 See <ref id="debianrules"> for information on how to get
2920 the architecture for the build process.
2924 <sect1 id="f-Essential">
2925 <heading><tt>Essential</tt></heading>
2928 This is a boolean field which may occur only in the
2929 control file of a binary package or in a per-package fields
2930 paragraph of a main source control data file.
2934 If set to <tt>yes</tt> then the package management system
2935 will refuse to remove the package (upgrading and replacing
2936 it is still possible). The other possible value is <tt>no</tt>,
2937 which is the same as not having the field at all.
2942 <heading>Package interrelationship fields:
2943 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2944 <tt>Recommends</tt>, <tt>Suggests</tt>,
2945 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2946 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2950 These fields describe the package's relationships with
2951 other packages. Their syntax and semantics are described
2952 in <ref id="relationships">.</p>
2955 <sect1 id="f-Standards-Version">
2956 <heading><tt>Standards-Version</tt></heading>
2959 The most recent version of the standards (the policy
2960 manual and associated texts) with which the package
2965 The version number has four components: major and minor
2966 version number and major and minor patch level. When the
2967 standards change in a way that requires every package to
2968 change the major number will be changed. Significant
2969 changes that will require work in many packages will be
2970 signaled by a change to the minor number. The major patch
2971 level will be changed for any change to the meaning of the
2972 standards, however small; the minor patch level will be
2973 changed when only cosmetic, typographical or other edits
2974 are made which neither change the meaning of the document
2975 nor affect the contents of packages.
2979 Thus only the first three components of the policy version
2980 are significant in the <em>Standards-Version</em> control
2981 field, and so either these three components or all four
2982 components may be specified.<footnote>
2983 In the past, people specified the full version number
2984 in the Standards-Version field, for example "2.3.0.0".
2985 Since minor patch-level changes don't introduce new
2986 policy, it was thought it would be better to relax
2987 policy and only require the first 3 components to be
2988 specified, in this example "2.3.0". All four
2989 components may still be used if someone wishes to do so.
2995 <sect1 id="f-Version">
2996 <heading><tt>Version</tt></heading>
2999 The version number of a package. The format is:
3000 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3004 The three components here are:
3006 <tag><var>epoch</var></tag>
3009 This is a single (generally small) unsigned integer. It
3010 may be omitted, in which case zero is assumed. If it is
3011 omitted then the <var>upstream_version</var> may not
3016 It is provided to allow mistakes in the version numbers
3017 of older versions of a package, and also a package's
3018 previous version numbering schemes, to be left behind.
3022 <tag><var>upstream_version</var></tag>
3025 This is the main part of the version number. It is
3026 usually the version number of the original ("upstream")
3027 package from which the <file>.deb</file> file has been made,
3028 if this is applicable. Usually this will be in the same
3029 format as that specified by the upstream author(s);
3030 however, it may need to be reformatted to fit into the
3031 package management system's format and comparison
3036 The comparison behavior of the package management system
3037 with respect to the <var>upstream_version</var> is
3038 described below. The <var>upstream_version</var>
3039 portion of the version number is mandatory.
3043 The <var>upstream_version</var> may contain only
3044 alphanumerics<footnote>
3045 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3047 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3048 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3049 tilde) and should start with a digit. If there is no
3050 <var>debian_revision</var> then hyphens are not allowed;
3051 if there is no <var>epoch</var> then colons are not
3056 <tag><var>debian_revision</var></tag>
3059 This part of the version number specifies the version of
3060 the Debian package based on the upstream version. It
3061 may contain only alphanumerics and the characters
3062 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3063 tilde) and is compared in the same way as the
3064 <var>upstream_version</var> is.
3068 It is optional; if it isn't present then the
3069 <var>upstream_version</var> may not contain a hyphen.
3070 This format represents the case where a piece of
3071 software was written specifically to be a Debian
3072 package, where the Debian package source must always
3073 be identical to the pristine source and therefore no
3074 revision indication is required.
3078 It is conventional to restart the
3079 <var>debian_revision</var> at <tt>1</tt> each time the
3080 <var>upstream_version</var> is increased.
3084 The package management system will break the version
3085 number apart at the last hyphen in the string (if there
3086 is one) to determine the <var>upstream_version</var> and
3087 <var>debian_revision</var>. The absence of a
3088 <var>debian_revision</var> is equivalent to a
3089 <var>debian_revision</var> of <tt>0</tt>.
3096 When comparing two version numbers, first the <var>epoch</var>
3097 of each are compared, then the <var>upstream_version</var> if
3098 <var>epoch</var> is equal, and then <var>debian_revision</var>
3099 if <var>upstream_version</var> is also equal.
3100 <var>epoch</var> is compared numerically. The
3101 <var>upstream_version</var> and <var>debian_revision</var>
3102 parts are compared by the package management system using the
3103 following algorithm:
3107 The strings are compared from left to right.
3111 First the initial part of each string consisting entirely of
3112 non-digit characters is determined. These two parts (one of
3113 which may be empty) are compared lexically. If a difference
3114 is found it is returned. The lexical comparison is a
3115 comparison of ASCII values modified so that all the letters
3116 sort earlier than all the non-letters and so that a tilde
3117 sorts before anything, even the end of a part. For example,
3118 the following parts are in sorted order from earliest to
3119 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3120 <tt>a</tt>.<footnote>
3121 One common use of <tt>~</tt> is for upstream pre-releases.
3122 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3123 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3128 Then the initial part of the remainder of each string which
3129 consists entirely of digit characters is determined. The
3130 numerical values of these two parts are compared, and any
3131 difference found is returned as the result of the comparison.
3132 For these purposes an empty string (which can only occur at
3133 the end of one or both version strings being compared) counts
3138 These two steps (comparing and removing initial non-digit
3139 strings and initial digit strings) are repeated until a
3140 difference is found or both strings are exhausted.
3144 Note that the purpose of epochs is to allow us to leave behind
3145 mistakes in version numbering, and to cope with situations
3146 where the version numbering scheme changes. It is
3147 <em>not</em> intended to cope with version numbers containing
3148 strings of letters which the package management system cannot
3149 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3150 silly orderings.<footnote>
3151 The author of this manual has heard of a package whose
3152 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3153 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3159 <sect1 id="f-Description">
3160 <heading><tt>Description</tt></heading>
3163 In a source or binary control file, the <tt>Description</tt>
3164 field contains a description of the binary package, consisting
3165 of two parts, the synopsis or the short description, and the
3166 long description. The field's format is as follows:
3171 Description: <single line synopsis>
3172 <extended description over several lines>
3177 The lines in the extended description can have these formats:
3183 Those starting with a single space are part of a paragraph.
3184 Successive lines of this form will be word-wrapped when
3185 displayed. The leading space will usually be stripped off.
3189 Those starting with two or more spaces. These will be
3190 displayed verbatim. If the display cannot be panned
3191 horizontally, the displaying program will line wrap them "hard"
3192 (i.e., without taking account of word breaks). If it can they
3193 will be allowed to trail off to the right. None, one or two
3194 initial spaces may be deleted, but the number of spaces
3195 deleted from each line will be the same (so that you can have
3196 indenting work correctly, for example).
3200 Those containing a single space followed by a single full stop
3201 character. These are rendered as blank lines. This is the
3202 <em>only</em> way to get a blank line<footnote>
3203 Completely empty lines will not be rendered as blank lines.
3204 Instead, they will cause the parser to think you're starting
3205 a whole new record in the control file, and will therefore
3206 likely abort with an error.
3211 Those containing a space, a full stop and some more characters.
3212 These are for future expansion. Do not use them.
3218 Do not use tab characters. Their effect is not predictable.
3222 See <ref id="descriptions"> for further information on this.
3226 In a <file>.changes</file> file, the <tt>Description</tt>
3227 field contains a summary of the descriptions for the packages
3228 being uploaded. For this case, the first line of the field
3229 value (the part on the same line as <tt>Description:</tt>) is
3230 always empty. The content of the field is expressed as
3231 continuation lines, one line per package. Each line is
3232 indented by one space and contains the name of a binary
3233 package, a space, a hyphen (<tt>-</tt>), a space, and the
3234 short description line from that package.
3238 <sect1 id="f-Distribution">
3239 <heading><tt>Distribution</tt></heading>
3242 In a <file>.changes</file> file or parsed changelog output
3243 this contains the (space-separated) name(s) of the
3244 distribution(s) where this version of the package should
3245 be installed. Valid distributions are determined by the
3246 archive maintainers.<footnote>
3247 Example distribution names in the Debian archive used in
3248 <file>.changes</file> files are:
3249 <taglist compact="compact">
3250 <tag><em>unstable</em></tag>
3252 This distribution value refers to the
3253 <em>developmental</em> part of the Debian distribution
3254 tree. Most new packages, new upstream versions of
3255 packages and bug fixes go into the <em>unstable</em>
3259 <tag><em>experimental</em></tag>
3261 The packages with this distribution value are deemed
3262 by their maintainers to be high risk. Oftentimes they
3263 represent early beta or developmental packages from
3264 various sources that the maintainers want people to
3265 try, but are not ready to be a part of the other parts
3266 of the Debian distribution tree.
3271 Others are used for updating stable releases or for
3272 security uploads. More information is available in the
3273 Debian Developer's Reference, section "The Debian
3277 The Debian archive software only supports listing a single
3278 distribution. Migration of packages to other distributions is
3279 handled outside of the upload process.
3284 <heading><tt>Date</tt></heading>
3287 This field includes the date the package was built or last
3288 edited. It must be in the same format as the <var>date</var>
3289 in a <file>debian/changelog</file> entry.
3293 The value of this field is usually extracted from the
3294 <file>debian/changelog</file> file - see
3295 <ref id="dpkgchangelog">).
3299 <sect1 id="f-Format">
3300 <heading><tt>Format</tt></heading>
3303 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3304 files, this field declares the format version of that file.
3305 The syntax of the field value is the same as that of
3306 a <qref id="f-Version">package version number</qref> except
3307 that no epoch or Debian revision is allowed. The format
3308 described in this document is <tt>&changesversion;</tt>.
3312 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3313 Debian source control</qref> files, this field declares the
3314 format of the source package. The field value is used by
3315 programs acting on a source package to interpret the list of
3316 files in the source package and determine how to unpack it.
3317 The syntax of the field value is a numeric major revision, a
3318 period, a numeric minor revision, and then an optional subtype
3319 after whitespace, which if specified is an alphanumeric word
3320 in parentheses. The subtype is optional in the syntax but may
3321 be mandatory for particular source format revisions.
3323 The source formats currently supported by the Debian archive
3324 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3325 and <tt>3.0 (quilt)</tt>.
3330 <sect1 id="f-Urgency">
3331 <heading><tt>Urgency</tt></heading>
3334 This is a description of how important it is to upgrade to
3335 this version from previous ones. It consists of a single
3336 keyword taking one of the values <tt>low</tt>,
3337 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3338 <tt>critical</tt><footnote>
3339 Other urgency values are supported with configuration
3340 changes in the archive software but are not used in Debian.
3341 The urgency affects how quickly a package will be considered
3342 for inclusion into the <tt>testing</tt> distribution and
3343 gives an indication of the importance of any fixes included
3344 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3345 treated as synonymous.
3346 </footnote> (not case-sensitive) followed by an optional
3347 commentary (separated by a space) which is usually in
3348 parentheses. For example:
3351 Urgency: low (HIGH for users of diversions)
3357 The value of this field is usually extracted from the
3358 <file>debian/changelog</file> file - see
3359 <ref id="dpkgchangelog">.
3363 <sect1 id="f-Changes">
3364 <heading><tt>Changes</tt></heading>
3367 This field contains the human-readable changes data, describing
3368 the differences between the last version and the current one.
3372 The first line of the field value (the part on the same line
3373 as <tt>Changes:</tt>) is always empty. The content of the
3374 field is expressed as continuation lines, with each line
3375 indented by at least one space. Blank lines must be
3376 represented by a line consisting only of a space and a full
3381 The value of this field is usually extracted from the
3382 <file>debian/changelog</file> file - see
3383 <ref id="dpkgchangelog">).
3387 Each version's change information should be preceded by a
3388 "title" line giving at least the version, distribution(s)
3389 and urgency, in a human-readable way.
3393 If data from several versions is being returned the entry
3394 for the most recent version should be returned first, and
3395 entries should be separated by the representation of a
3396 blank line (the "title" line may also be followed by the
3397 representation of a blank line).
3401 <sect1 id="f-Binary">
3402 <heading><tt>Binary</tt></heading>
3405 This field is a list of binary packages. Its syntax and
3406 meaning varies depending on the control file in which it
3411 When it appears in the <file>.dsc</file> file, it lists binary
3412 packages which a source package can produce, separated by
3414 A space after each comma is conventional.
3415 </footnote>. It may span multiple lines. The source package
3416 does not necessarily produce all of these binary packages for
3417 every architecture. The source control file doesn't contain
3418 details of which architectures are appropriate for which of
3419 the binary packages.
3423 When it appears in a <file>.changes</file> file, it lists the
3424 names of the binary packages being uploaded, separated by
3425 whitespace (not commas). It may span multiple lines.
3429 <sect1 id="f-Installed-Size">
3430 <heading><tt>Installed-Size</tt></heading>
3433 This field appears in the control files of binary packages,
3434 and in the <file>Packages</file> files. It gives an estimate
3435 of the total amount of disk space required to install the
3436 named package. Actual installed size may vary based on block
3437 size, file system properties, or actions taken by package
3442 The disk space is given as the integer value of the estimated
3443 installed size in bytes, divided by 1024 and rounded up.
3447 <sect1 id="f-Files">
3448 <heading><tt>Files</tt></heading>
3451 This field contains a list of files with information about
3452 each one. The exact information and syntax varies with
3457 In all cases, Files is a multiline field. The first line of
3458 the field value (the part on the same line as <tt>Files:</tt>)
3459 is always empty. The content of the field is expressed as
3460 continuation lines, one line per file. Each line must be
3461 indented by one space and contain a number of sub-fields,
3462 separated by spaces, as described below.
3466 In the <file>.dsc</file> file, each line contains the MD5
3467 checksum, size and filename of the tar file and (if
3468 applicable) diff file which make up the remainder of the
3469 source package<footnote>
3470 That is, the parts which are not the <tt>.dsc</tt>.
3471 </footnote>. For example:
3474 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3475 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3477 The exact forms of the filenames are described
3478 in <ref id="pkg-sourcearchives">.
3482 In the <file>.changes</file> file this contains one line per
3483 file being uploaded. Each line contains the MD5 checksum,
3484 size, section and priority and the filename. For example:
3487 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3488 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3489 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3490 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3492 The <qref id="f-Section">section</qref>
3493 and <qref id="f-Priority">priority</qref> are the values of
3494 the corresponding fields in the main source control file. If
3495 no section or priority is specified then <tt>-</tt> should be
3496 used, though section and priority values must be specified for
3497 new packages to be installed properly.
3501 The special value <tt>byhand</tt> for the section in a
3502 <tt>.changes</tt> file indicates that the file in question
3503 is not an ordinary package file and must by installed by
3504 hand by the distribution maintainers. If the section is
3505 <tt>byhand</tt> the priority should be <tt>-</tt>.
3509 If a new Debian revision of a package is being shipped and
3510 no new original source archive is being distributed the
3511 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3512 entry for the original source archive
3513 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3514 but the <file>.changes</file> file should leave it out. In
3515 this case the original source archive on the distribution
3516 site must match exactly, byte-for-byte, the original
3517 source archive which was used to generate the
3518 <file>.dsc</file> file and diff which are being uploaded.</p>
3521 <sect1 id="f-Closes">
3522 <heading><tt>Closes</tt></heading>
3525 A space-separated list of bug report numbers that the upload
3526 governed by the .changes file closes.
3530 <sect1 id="f-Homepage">
3531 <heading><tt>Homepage</tt></heading>
3534 The URL of the web site for this package, preferably (when
3535 applicable) the site from which the original source can be
3536 obtained and any additional upstream documentation or
3537 information may be found. The content of this field is a
3538 simple URL without any surrounding characters such as
3543 <sect1 id="f-Checksums">
3544 <heading><tt>Checksums-Sha1</tt>
3545 and <tt>Checksums-Sha256</tt></heading>
3548 These fields contain a list of files with a checksum and size
3549 for each one. Both <tt>Checksums-Sha1</tt>
3550 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3551 only in the checksum algorithm used: SHA-1
3552 for <tt>Checksums-Sha1</tt> and SHA-256
3553 for <tt>Checksums-Sha256</tt>.
3557 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3558 multiline fields. The first line of the field value (the part
3559 on the same line as <tt>Checksums-Sha1:</tt>
3560 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3561 of the field is expressed as continuation lines, one line per
3562 file. Each line consists of the checksum, a space, the file
3563 size, a space, and the file name. For example (from
3564 a <file>.changes</file> file):
3567 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3568 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3569 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3570 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3572 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3573 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3574 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3575 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3580 In the <file>.dsc</file> file, these fields should list all
3581 files that make up the source package. In
3582 the <file>.changes</file> file, these fields should list all
3583 files being uploaded. The list of files in these fields
3584 must match the list of files in the <tt>Files</tt> field.
3590 <heading>User-defined fields</heading>
3593 Additional user-defined fields may be added to the
3594 source package control file. Such fields will be
3595 ignored, and not copied to (for example) binary or
3596 source package control files or upload control files.
3600 If you wish to add additional unsupported fields to
3601 these output files you should use the mechanism
3606 Fields in the main source control information file with
3607 names starting <tt>X</tt>, followed by one or more of
3608 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3609 be copied to the output files. Only the part of the
3610 field name after the hyphen will be used in the output
3611 file. Where the letter <tt>B</tt> is used the field
3612 will appear in binary package control files, where the
3613 letter <tt>S</tt> is used in source package control
3614 files and where <tt>C</tt> is used in upload control
3615 (<tt>.changes</tt>) files.
3619 For example, if the main source information control file
3622 XBS-Comment: I stand between the candle and the star.
3624 then the binary and source package control files will contain the
3627 Comment: I stand between the candle and the star.
3636 <chapt id="maintainerscripts">
3637 <heading>Package maintainer scripts and installation procedure</heading>
3640 <heading>Introduction to package maintainer scripts</heading>
3643 It is possible to supply scripts as part of a package which
3644 the package management system will run for you when your
3645 package is installed, upgraded or removed.
3649 These scripts are the control information
3650 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3651 and <prgn>postrm</prgn>. They must be proper executable files;
3652 if they are scripts (which is recommended), they must start with
3653 the usual <tt>#!</tt> convention. They should be readable and
3654 executable by anyone, and must not be world-writable.
3658 The package management system looks at the exit status from
3659 these scripts. It is important that they exit with a
3660 non-zero status if there is an error, so that the package
3661 management system can stop its processing. For shell
3662 scripts this means that you <em>almost always</em> need to
3663 use <tt>set -e</tt> (this is usually true when writing shell
3664 scripts, in fact). It is also important, of course, that
3665 they exit with a zero status if everything went well.
3669 Additionally, packages interacting with users
3670 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3671 should install a <prgn>config</prgn> script as a control
3672 information file. See <ref id="maintscriptprompt"> for details.
3676 When a package is upgraded a combination of the scripts from
3677 the old and new packages is called during the upgrade
3678 procedure. If your scripts are going to be at all
3679 complicated you need to be aware of this, and may need to
3680 check the arguments to your scripts.
3684 Broadly speaking the <prgn>preinst</prgn> is called before
3685 (a particular version of) a package is installed, and the
3686 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3687 before (a version of) a package is removed and the
3688 <prgn>postrm</prgn> afterwards.
3692 Programs called from maintainer scripts should not normally
3693 have a path prepended to them. Before installation is
3694 started, the package management system checks to see if the
3695 programs <prgn>ldconfig</prgn>,
3696 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3697 and <prgn>update-rc.d</prgn> can be found via the
3698 <tt>PATH</tt> environment variable. Those programs, and any
3699 other program that one would expect to be in the
3700 <tt>PATH</tt>, should thus be invoked without an absolute
3701 pathname. Maintainer scripts should also not reset the
3702 <tt>PATH</tt>, though they might choose to modify it by
3703 prepending or appending package-specific directories. These
3704 considerations really apply to all shell scripts.</p>
3707 <sect id="idempotency">
3708 <heading>Maintainer scripts idempotency</heading>
3711 It is necessary for the error recovery procedures that the
3712 scripts be idempotent. This means that if it is run
3713 successfully, and then it is called again, it doesn't bomb
3714 out or cause any harm, but just ensures that everything is
3715 the way it ought to be. If the first call failed, or
3716 aborted half way through for some reason, the second call
3717 should merely do the things that were left undone the first
3718 time, if any, and exit with a success status if everything
3720 This is so that if an error occurs, the user interrupts
3721 <prgn>dpkg</prgn> or some other unforeseen circumstance
3722 happens you don't leave the user with a badly-broken
3723 package when <prgn>dpkg</prgn> attempts to repeat the
3729 <sect id="controllingterminal">
3730 <heading>Controlling terminal for maintainer scripts</heading>
3733 Maintainer scripts are not guaranteed to run with a controlling
3734 terminal and may not be able to interact with the user. They
3735 must be able to fall back to noninteractive behavior if no
3736 controlling terminal is available. Maintainer scripts that
3737 prompt via a program conforming to the Debian Configuration
3738 Management Specification (see <ref id="maintscriptprompt">) may
3739 assume that program will handle falling back to noninteractive
3744 For high-priority prompts without a reasonable default answer,
3745 maintainer scripts may abort if there is no controlling
3746 terminal. However, this situation should be avoided if at all
3747 possible, since it prevents automated or unattended installs.
3748 In most cases, users will consider this to be a bug in the
3753 <sect id="exitstatus">
3754 <heading>Exit status</heading>
3757 Each script must return a zero exit status for
3758 success, or a nonzero one for failure, since the package
3759 management system looks for the exit status of these scripts
3760 and determines what action to take next based on that datum.
3764 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3769 <list compact="compact">
3771 <var>new-preinst</var> <tt>install</tt>
3774 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3777 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3780 <var>old-preinst</var> <tt>abort-upgrade</tt>
3781 <var>new-version</var>
3786 <list compact="compact">
3788 <var>postinst</var> <tt>configure</tt>
3789 <var>most-recently-configured-version</var>
3792 <var>old-postinst</var> <tt>abort-upgrade</tt>
3793 <var>new-version</var>
3796 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3797 <tt>in-favour</tt> <var>package</var>
3798 <var>new-version</var>
3801 <var>postinst</var> <tt>abort-remove</tt>
3804 <var>deconfigured's-postinst</var>
3805 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3806 <var>failed-install-package</var> <var>version</var>
3807 [<tt>removing</tt> <var>conflicting-package</var>
3813 <list compact="compact">
3815 <var>prerm</var> <tt>remove</tt>
3818 <var>old-prerm</var> <tt>upgrade</tt>
3819 <var>new-version</var>
3822 <var>new-prerm</var> <tt>failed-upgrade</tt>
3823 <var>old-version</var>
3826 <var>conflictor's-prerm</var> <tt>remove</tt>
3827 <tt>in-favour</tt> <var>package</var>
3828 <var>new-version</var>
3831 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3832 <tt>in-favour</tt> <var>package-being-installed</var>
3833 <var>version</var> [<tt>removing</tt>
3834 <var>conflicting-package</var>
3840 <list compact="compact">
3842 <var>postrm</var> <tt>remove</tt>
3845 <var>postrm</var> <tt>purge</tt>
3848 <var>old-postrm</var> <tt>upgrade</tt>
3849 <var>new-version</var>
3852 <var>new-postrm</var> <tt>failed-upgrade</tt>
3853 <var>old-version</var>
3856 <var>new-postrm</var> <tt>abort-install</tt>
3859 <var>new-postrm</var> <tt>abort-install</tt>
3860 <var>old-version</var>
3863 <var>new-postrm</var> <tt>abort-upgrade</tt>
3864 <var>old-version</var>
3867 <var>disappearer's-postrm</var> <tt>disappear</tt>
3868 <var>overwriter</var>
3869 <var>overwriter-version</var>
3875 <sect id="unpackphase">
3876 <heading>Details of unpack phase of installation or upgrade</heading>
3879 The procedure on installation/upgrade/overwrite/disappear
3880 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3881 stage of <tt>dpkg --install</tt>) is as follows. In each
3882 case, if a major error occurs (unless listed below) the
3883 actions are, in general, run backwards - this means that the
3884 maintainer scripts are run with different arguments in
3885 reverse order. These are the "error unwind" calls listed
3892 If a version of the package is already installed, call
3893 <example compact="compact">
3894 <var>old-prerm</var> upgrade <var>new-version</var>
3898 If the script runs but exits with a non-zero
3899 exit status, <prgn>dpkg</prgn> will attempt:
3900 <example compact="compact">
3901 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3903 If this works, the upgrade continues. If this
3904 does not work, the error unwind:
3905 <example compact="compact">
3906 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3908 If this works, then the old-version is
3909 "Installed", if not, the old version is in a
3910 "Half-Configured" state.
3916 If a "conflicting" package is being removed at the same time,
3917 or if any package will be broken (due to <tt>Breaks</tt>):
3920 If <tt>--auto-deconfigure</tt> is
3921 specified, call, for each package to be deconfigured
3922 due to <tt>Breaks</tt>:
3923 <example compact="compact">
3924 <var>deconfigured's-prerm</var> deconfigure \
3925 in-favour <var>package-being-installed</var> <var>version</var>
3928 <example compact="compact">
3929 <var>deconfigured's-postinst</var> abort-deconfigure \
3930 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3932 The deconfigured packages are marked as
3933 requiring configuration, so that if
3934 <tt>--install</tt> is used they will be
3935 configured again if possible.
3938 If any packages depended on a conflicting
3939 package being removed and <tt>--auto-deconfigure</tt> is
3940 specified, call, for each such package:
3941 <example compact="compact">
3942 <var>deconfigured's-prerm</var> deconfigure \
3943 in-favour <var>package-being-installed</var> <var>version</var> \
3944 removing <var>conflicting-package</var> <var>version</var>
3947 <example compact="compact">
3948 <var>deconfigured's-postinst</var> abort-deconfigure \
3949 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3950 removing <var>conflicting-package</var> <var>version</var>
3952 The deconfigured packages are marked as
3953 requiring configuration, so that if
3954 <tt>--install</tt> is used they will be
3955 configured again if possible.
3958 To prepare for removal of each conflicting package, call:
3959 <example compact="compact">
3960 <var>conflictor's-prerm</var> remove \
3961 in-favour <var>package</var> <var>new-version</var>
3964 <example compact="compact">
3965 <var>conflictor's-postinst</var> abort-remove \
3966 in-favour <var>package</var> <var>new-version</var>
3975 If the package is being upgraded, call:
3976 <example compact="compact">
3977 <var>new-preinst</var> upgrade <var>old-version</var>
3979 If this fails, we call:
3981 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3988 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3990 is called. If this works, then the old version
3991 is in an "Installed" state, or else it is left
3992 in an "Unpacked" state.
3997 If it fails, then the old version is left
3998 in an "Half-Installed" state.
4005 Otherwise, if the package had some configuration
4006 files from a previous version installed (i.e., it
4007 is in the "configuration files only" state):
4008 <example compact="compact">
4009 <var>new-preinst</var> install <var>old-version</var>
4013 <var>new-postrm</var> abort-install <var>old-version</var>
4015 If this fails, the package is left in a
4016 "Half-Installed" state, which requires a
4017 reinstall. If it works, the packages is left in
4018 a "Config-Files" state.
4021 Otherwise (i.e., the package was completely purged):
4022 <example compact="compact">
4023 <var>new-preinst</var> install
4026 <example compact="compact">
4027 <var>new-postrm</var> abort-install
4029 If the error-unwind fails, the package is in a
4030 "Half-Installed" phase, and requires a
4031 reinstall. If the error unwind works, the
4032 package is in a not installed state.
4039 The new package's files are unpacked, overwriting any
4040 that may be on the system already, for example any
4041 from the old version of the same package or from
4042 another package. Backups of the old files are kept
4043 temporarily, and if anything goes wrong the package
4044 management system will attempt to put them back as
4045 part of the error unwind.
4049 It is an error for a package to contain files which
4050 are on the system in another package, unless
4051 <tt>Replaces</tt> is used (see <ref id="replaces">).
4053 The following paragraph is not currently the case:
4054 Currently the <tt>- - force-overwrite</tt> flag is
4055 enabled, downgrading it to a warning, but this may not
4061 It is a more serious error for a package to contain a
4062 plain file or other kind of non-directory where another
4063 package has a directory (again, unless
4064 <tt>Replaces</tt> is used). This error can be
4065 overridden if desired using
4066 <tt>--force-overwrite-dir</tt>, but this is not
4071 Packages which overwrite each other's files produce
4072 behavior which, though deterministic, is hard for the
4073 system administrator to understand. It can easily
4074 lead to "missing" programs if, for example, a package
4075 is installed which overwrites a file from another
4076 package, and is then removed again.<footnote>
4077 Part of the problem is due to what is arguably a
4078 bug in <prgn>dpkg</prgn>.
4083 A directory will never be replaced by a symbolic link
4084 to a directory or vice versa; instead, the existing
4085 state (symlink or not) will be left alone and
4086 <prgn>dpkg</prgn> will follow the symlink if there is
4095 If the package is being upgraded, call
4096 <example compact="compact">
4097 <var>old-postrm</var> upgrade <var>new-version</var>
4101 If this fails, <prgn>dpkg</prgn> will attempt:
4102 <example compact="compact">
4103 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4105 If this works, installation continues. If not,
4107 <example compact="compact">
4108 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4110 If this fails, the old version is left in a
4111 "Half-Installed" state. If it works, dpkg now
4113 <example compact="compact">
4114 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4116 If this fails, the old version is left in a
4117 "Half-Installed" state. If it works, dpkg now
4119 <example compact="compact">
4120 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4122 If this fails, the old version is in an
4129 This is the point of no return - if
4130 <prgn>dpkg</prgn> gets this far, it won't back off
4131 past this point if an error occurs. This will
4132 leave the package in a fairly bad state, which
4133 will require a successful re-installation to clear
4134 up, but it's when <prgn>dpkg</prgn> starts doing
4135 things that are irreversible.
4140 Any files which were in the old version of the package
4141 but not in the new are removed.
4145 The new file list replaces the old.
4149 The new maintainer scripts replace the old.
4153 Any packages all of whose files have been overwritten
4154 during the installation, and which aren't required for
4155 dependencies, are considered to have been removed.
4156 For each such package
4159 <prgn>dpkg</prgn> calls:
4160 <example compact="compact">
4161 <var>disappearer's-postrm</var> disappear \
4162 <var>overwriter</var> <var>overwriter-version</var>
4166 The package's maintainer scripts are removed.
4169 It is noted in the status database as being in a
4170 sane state, namely not installed (any conffiles
4171 it may have are ignored, rather than being
4172 removed by <prgn>dpkg</prgn>). Note that
4173 disappearing packages do not have their prerm
4174 called, because <prgn>dpkg</prgn> doesn't know
4175 in advance that the package is going to
4182 Any files in the package we're unpacking that are also
4183 listed in the file lists of other packages are removed
4184 from those lists. (This will lobotomize the file list
4185 of the "conflicting" package if there is one.)
4189 The backup files made during installation, above, are
4195 The new package's status is now sane, and recorded as
4200 Here is another point of no return - if the
4201 conflicting package's removal fails we do not unwind
4202 the rest of the installation; the conflicting package
4203 is left in a half-removed limbo.
4208 If there was a conflicting package we go and do the
4209 removal actions (described below), starting with the
4210 removal of the conflicting package's files (any that
4211 are also in the package being installed have already
4212 been removed from the conflicting package's file list,
4213 and so do not get removed now).
4219 <sect id="configdetails"><heading>Details of configuration</heading>
4222 When we configure a package (this happens with <tt>dpkg
4223 --install</tt> and <tt>dpkg --configure</tt>), we first
4224 update any <tt>conffile</tt>s and then call:
4225 <example compact="compact">
4226 <var>postinst</var> configure <var>most-recently-configured-version</var>
4231 No attempt is made to unwind after errors during
4232 configuration. If the configuration fails, the package is in
4233 a "Failed Config" state, and an error message is generated.
4237 If there is no most recently configured version
4238 <prgn>dpkg</prgn> will pass a null argument.
4241 Historical note: Truly ancient (pre-1997) versions of
4242 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4243 (including the angle brackets) in this case. Even older
4244 ones did not pass a second argument at all, under any
4245 circumstance. Note that upgrades using such an old dpkg
4246 version are unlikely to work for other reasons, even if
4247 this old argument behavior is handled by your postinst script.
4253 <sect id="removedetails"><heading>Details of removal and/or
4254 configuration purging</heading>
4260 <example compact="compact">
4261 <var>prerm</var> remove
4265 If prerm fails during replacement due to conflict
4267 <var>conflictor's-postinst</var> abort-remove \
4268 in-favour <var>package</var> <var>new-version</var>
4272 <var>postinst</var> abort-remove
4276 If this fails, the package is in a "Half-Configured"
4277 state, or else it remains "Installed".
4281 The package's files are removed (except <tt>conffile</tt>s).
4284 <example compact="compact">
4285 <var>postrm</var> remove
4289 If it fails, there's no error unwind, and the package is in
4290 an "Half-Installed" state.
4295 All the maintainer scripts except the <prgn>postrm</prgn>
4300 If we aren't purging the package we stop here. Note
4301 that packages which have no <prgn>postrm</prgn> and no
4302 <tt>conffile</tt>s are automatically purged when
4303 removed, as there is no difference except for the
4304 <prgn>dpkg</prgn> status.
4308 The <tt>conffile</tt>s and any backup files
4309 (<tt>~</tt>-files, <tt>#*#</tt> files,
4310 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4315 <example compact="compact">
4316 <var>postrm</var> purge
4320 If this fails, the package remains in a "Config-Files"
4325 The package's file list is removed.
4334 <chapt id="relationships">
4335 <heading>Declaring relationships between packages</heading>
4337 <sect id="depsyntax">
4338 <heading>Syntax of relationship fields</heading>
4341 These fields all have a uniform syntax. They are a list of
4342 package names separated by commas.
4346 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4347 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4348 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4349 control fields of the package, which declare
4350 dependencies on other packages, the package names listed may
4351 also include lists of alternative package names, separated
4352 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4353 if any one of the alternative packages is installed, that
4354 part of the dependency is considered to be satisfied.
4358 All of the fields except for <tt>Provides</tt> may restrict
4359 their applicability to particular versions of each named
4360 package. This is done in parentheses after each individual
4361 package name; the parentheses should contain a relation from
4362 the list below followed by a version number, in the format
4363 described in <ref id="f-Version">.
4367 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4368 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4369 strictly earlier, earlier or equal, exactly equal, later or
4370 equal and strictly later, respectively. The deprecated
4371 forms <tt><</tt> and <tt>></tt> were used to mean
4372 earlier/later or equal, rather than strictly earlier/later,
4373 so they should not appear in new packages (though
4374 <prgn>dpkg</prgn> still supports them).
4378 Whitespace may appear at any point in the version
4379 specification subject to the rules in <ref
4380 id="controlsyntax">, and must appear where it's necessary to
4381 disambiguate; it is not otherwise significant. All of the
4382 relationship fields may span multiple lines. For
4383 consistency and in case of future changes to
4384 <prgn>dpkg</prgn> it is recommended that a single space be
4385 used after a version relationship and before a version
4386 number; it is also conventional to put a single space after
4387 each comma, on either side of each vertical bar, and before
4388 each open parenthesis. When wrapping a relationship field, it
4389 is conventional to do so after a comma and before the space
4390 following that comma.
4394 For example, a list of dependencies might appear as:
4395 <example compact="compact">
4398 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4403 Relationships may be restricted to a certain set of
4404 architectures. This is indicated in brackets after each
4405 individual package name and the optional version specification.
4406 The brackets enclose a list of Debian architecture names
4407 separated by whitespace. Exclamation marks may be prepended to
4408 each of the names. (It is not permitted for some names to be
4409 prepended with exclamation marks while others aren't.)
4413 For build relationship fields
4414 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4415 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4416 the current Debian host architecture is not in this list and
4417 there are no exclamation marks in the list, or it is in the list
4418 with a prepended exclamation mark, the package name and the
4419 associated version specification are ignored completely for the
4420 purposes of defining the relationships.
4425 <example compact="compact">
4427 Build-Depends-Indep: texinfo
4428 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4429 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4431 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4432 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4433 <tt>gnumach-dev</tt> only on hurd-i386.
4437 For binary relationship fields, the architecture restriction
4438 syntax is only supported in the source package control
4439 file <file>debian/control</file>. When the corresponding binary
4440 package control file is generated, the relationship will either
4441 be omitted or included without the architecture restriction
4442 based on the architecture of the binary package. This means
4443 that architecture restrictions must not be used in binary
4444 relationship fields for architecture-independent packages
4445 (<tt>Architecture: all</tt>).
4450 <example compact="compact">
4451 Depends: foo [i386], bar [amd64]
4453 becomes <tt>Depends: foo</tt> when the package is built on
4454 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4455 package is built on the <tt>amd64</tt> architecture, and omitted
4456 entirely in binary packages built on all other architectures.
4460 If the architecture-restricted dependency is part of a set of
4461 alternatives using <tt>|</tt>, that alternative is ignored
4462 completely on architectures that do not match the restriction.
4464 <example compact="compact">
4465 Build-Depends: foo [!i386] | bar [!amd64]
4467 is equivalent to <tt>bar</tt> on the i386 architecture, to
4468 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4469 bar</tt> on all other architectures.
4473 Relationships may also be restricted to a certain set of
4474 architectures using architecture wildcards. The syntax for
4475 declaring such restrictions is the same as declaring
4476 restrictions using a certain set of architectures without
4477 architecture wildcards. For example:
4478 <example compact="compact">
4479 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4481 is equivalent to <tt>foo</tt> on architectures using the Linux
4482 kernel and any cpu, <tt>bar</tt> on architectures using any
4483 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4484 using a kernel other than Linux.
4488 Note that the binary package relationship fields such as
4489 <tt>Depends</tt> appear in one of the binary package
4490 sections of the control file, whereas the build-time
4491 relationships such as <tt>Build-Depends</tt> appear in the
4492 source package section of the control file (which is the
4497 <sect id="binarydeps">
4498 <heading>Binary Dependencies - <tt>Depends</tt>,
4499 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4500 <tt>Pre-Depends</tt>
4504 Packages can declare in their control file that they have
4505 certain relationships to other packages - for example, that
4506 they may not be installed at the same time as certain other
4507 packages, and/or that they depend on the presence of others.
4511 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4512 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4513 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4514 <tt>Breaks</tt> is described in <ref id="breaks">, and
4515 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4516 rest are described below.
4520 These seven fields are used to declare a dependency
4521 relationship by one package on another. Except for
4522 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4523 depending (binary) package's control file.
4524 (<tt>Enhances</tt> appears in the recommending package's
4525 control file, and <tt>Breaks</tt> appears in the version of
4526 depended-on package which causes the named package to
4531 A <tt>Depends</tt> field takes effect <em>only</em> when a
4532 package is to be configured. It does not prevent a package
4533 being on the system in an unconfigured state while its
4534 dependencies are unsatisfied, and it is possible to replace
4535 a package whose dependencies are satisfied and which is
4536 properly installed with a different version whose
4537 dependencies are not and cannot be satisfied; when this is
4538 done the depending package will be left unconfigured (since
4539 attempts to configure it will give errors) and will not
4540 function properly. If it is necessary, a
4541 <tt>Pre-Depends</tt> field can be used, which has a partial
4542 effect even when a package is being unpacked, as explained
4543 in detail below. (The other three dependency fields,
4544 <tt>Recommends</tt>, <tt>Suggests</tt> and
4545 <tt>Enhances</tt>, are only used by the various front-ends
4546 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4547 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4551 For this reason packages in an installation run are usually
4552 all unpacked first and all configured later; this gives
4553 later versions of packages with dependencies on later
4554 versions of other packages the opportunity to have their
4555 dependencies satisfied.
4559 In case of circular dependencies, since installation or
4560 removal order honoring the dependency order can't be
4561 established, dependency loops are broken at some point
4562 (based on rules below), and some packages may not be able to
4563 rely on their dependencies being present when being
4564 installed or removed, depending on which side of the break
4565 of the circular dependency loop they happen to be on. If one
4566 of the packages in the loop has no postinst script, then the
4567 cycle will be broken at that package, so as to ensure that
4568 all postinst scripts run with the dependencies properly
4569 configured if this is possible. Otherwise the breaking point
4574 The <tt>Depends</tt> field thus allows package maintainers
4575 to impose an order in which packages should be configured.
4579 The meaning of the five dependency fields is as follows:
4581 <tag><tt>Depends</tt></tag>
4584 This declares an absolute dependency. A package will
4585 not be configured unless all of the packages listed in
4586 its <tt>Depends</tt> field have been correctly
4591 The <tt>Depends</tt> field should be used if the
4592 depended-on package is required for the depending
4593 package to provide a significant amount of
4598 The <tt>Depends</tt> field should also be used if the
4599 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4600 <prgn>postrm</prgn> scripts require the package to be
4601 present in order to run. Note, however, that the
4602 <prgn>postrm</prgn> cannot rely on any non-essential
4603 packages to be present during the <tt>purge</tt>
4607 <tag><tt>Recommends</tt></tag>
4610 This declares a strong, but not absolute, dependency.
4614 The <tt>Recommends</tt> field should list packages
4615 that would be found together with this one in all but
4616 unusual installations.
4620 <tag><tt>Suggests</tt></tag>
4622 This is used to declare that one package may be more
4623 useful with one or more others. Using this field
4624 tells the packaging system and the user that the
4625 listed packages are related to this one and can
4626 perhaps enhance its usefulness, but that installing
4627 this one without them is perfectly reasonable.
4630 <tag><tt>Enhances</tt></tag>
4632 This field is similar to Suggests but works in the
4633 opposite direction. It is used to declare that a
4634 package can enhance the functionality of another
4638 <tag><tt>Pre-Depends</tt></tag>
4641 This field is like <tt>Depends</tt>, except that it
4642 also forces <prgn>dpkg</prgn> to complete installation
4643 of the packages named before even starting the
4644 installation of the package which declares the
4645 pre-dependency, as follows:
4649 When a package declaring a pre-dependency is about to
4650 be <em>unpacked</em> the pre-dependency can be
4651 satisfied if the depended-on package is either fully
4652 configured, <em>or even if</em> the depended-on
4653 package(s) are only unpacked or in the "Half-Configured"
4654 state, provided that they have been configured
4655 correctly at some point in the past (and not removed
4656 or partially removed since). In this case, both the
4657 previously-configured and currently unpacked or
4658 "Half-Configured" versions must satisfy any version
4659 clause in the <tt>Pre-Depends</tt> field.
4663 When the package declaring a pre-dependency is about
4664 to be <em>configured</em>, the pre-dependency will be
4665 treated as a normal <tt>Depends</tt>, that is, it will
4666 be considered satisfied only if the depended-on
4667 package has been correctly configured.
4671 <tt>Pre-Depends</tt> should be used sparingly,
4672 preferably only by packages whose premature upgrade or
4673 installation would hamper the ability of the system to
4674 continue with any upgrade that might be in progress.
4678 <tt>Pre-Depends</tt> are also required if the
4679 <prgn>preinst</prgn> script depends on the named
4680 package. It is best to avoid this situation if
4688 When selecting which level of dependency to use you should
4689 consider how important the depended-on package is to the
4690 functionality of the one declaring the dependency. Some
4691 packages are composed of components of varying degrees of
4692 importance. Such a package should list using
4693 <tt>Depends</tt> the package(s) which are required by the
4694 more important components. The other components'
4695 requirements may be mentioned as Suggestions or
4696 Recommendations, as appropriate to the components' relative
4702 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4705 When one binary package declares that it breaks another,
4706 <prgn>dpkg</prgn> will refuse to allow the package which
4707 declares <tt>Breaks</tt> be installed unless the broken
4708 package is deconfigured first, and it will refuse to
4709 allow the broken package to be reconfigured.
4713 A package will not be regarded as causing breakage merely
4714 because its configuration files are still installed; it must
4715 be at least "Half-Installed".
4719 A special exception is made for packages which declare that
4720 they break their own package name or a virtual package which
4721 they provide (see below): this does not count as a real
4726 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4727 version clause; such a <tt>Breaks</tt> is introduced in the
4728 version of an (implicit or explicit) dependency which violates
4729 an assumption or reveals a bug in earlier versions of the broken
4730 package, or which takes over a file from earlier versions of the
4731 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4732 will inform higher-level package management tools that the
4733 broken package must be upgraded before the new one.
4737 If the breaking package also overwrites some files from the
4738 older package, it should use <tt>Replaces</tt> to ensure this
4739 goes smoothly. See <ref id="replaces"> for a full discussion
4740 of taking over files from other packages, including how to
4741 use <tt>Breaks</tt> in those cases.
4745 Many of the cases where <tt>Breaks</tt> should be used were
4746 previously handled with <tt>Conflicts</tt>
4747 because <tt>Breaks</tt> did not yet exist.
4748 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4749 See <ref id="conflicts"> for more information about the
4754 <sect id="conflicts">
4755 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4758 When one binary package declares a conflict with another
4759 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4760 refuse to allow them to be installed on the system at the
4761 same time. This is a stronger restriction than <tt>Breaks</tt>,
4762 which just prevents both packages from being configured at the
4763 same time. Conflicting packages cannot be unpacked on the
4764 system at the same time.
4768 If one package is to be installed, the other must be removed
4769 first. If the package being installed is marked as replacing
4770 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4771 normally be used in this case) the one on the system, or the one
4772 on the system is marked as deselected, or both packages are
4773 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4774 automatically remove the package which is causing the conflict.
4775 Otherwise, it will halt the installation of the new package with
4776 an error. This mechanism is specifically designed to produce an
4777 error when the installed package is <tt>Essential</tt>, but the
4782 A package will not cause a conflict merely because its
4783 configuration files are still installed; it must be at least
4788 A special exception is made for packages which declare a
4789 conflict with their own package name, or with a virtual
4790 package which they provide (see below): this does not
4791 prevent their installation, and allows a package to conflict
4792 with others providing a replacement for it. You use this
4793 feature when you want the package in question to be the only
4794 package providing some feature.
4798 Normally, <tt>Breaks</tt> should be used instead
4799 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4800 stronger restriction on the ordering of package installation or
4801 upgrade and can make it more difficult for the package manager
4802 to find a correct solution to an upgrade or installation
4803 problem. <tt>Breaks</tt> should be used
4805 <item>when moving a file from one package to another (see
4806 <ref id="replaces">),</item>
4807 <item>when splitting a package (a special case of the previous
4809 <item>when the breaking package exposes a bug in or interacts
4810 badly with particular versions of the broken
4813 <tt>Conflicts</tt> should be used
4815 <item>when two packages provide the same file and will
4816 continue to do so,</item>
4817 <item>in conjunction with <tt>Provides</tt> when only one
4818 package providing a given virtual facility may be installed
4819 at a time (see <ref id="virtual">),</item>
4820 <item>in other cases where one must prevent simultaneous
4821 installation of two packages for reasons that are ongoing
4822 (not fixed in a later version of one of the packages) or
4823 that must prevent both packages from being unpacked at the
4824 same time, not just configured.</item>
4826 Be aware that adding <tt>Conflicts</tt> is normally not the best
4827 solution when two packages provide the same files. Depending on
4828 the reason for that conflict, using alternatives or renaming the
4829 files is often a better approach. See, for
4830 example, <ref id="binaries">.
4834 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4835 unless two packages cannot be installed at the same time or
4836 installing them both causes one of them to be broken or
4837 unusable. Having similar functionality or performing the same
4838 tasks as another package is not sufficient reason to
4839 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4843 A <tt>Conflicts</tt> entry may have an "earlier than" version
4844 clause if the reason for the conflict is corrected in a later
4845 version of one of the packages. However, normally the presence
4846 of an "earlier than" version clause is a sign
4847 that <tt>Breaks</tt> should have been used instead. An "earlier
4848 than" version clause in <tt>Conflicts</tt>
4849 prevents <prgn>dpkg</prgn> from upgrading or installing the
4850 package which declares such a conflict until the upgrade or
4851 removal of the conflicted-with package has been completed, which
4852 is a strong restriction.
4856 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4860 As well as the names of actual ("concrete") packages, the
4861 package relationship fields <tt>Depends</tt>,
4862 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4863 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4864 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4865 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4866 may mention "virtual packages".
4870 A <em>virtual package</em> is one which appears in the
4871 <tt>Provides</tt> control field of another package. The effect
4872 is as if the package(s) which provide a particular virtual
4873 package name had been listed by name everywhere the virtual
4874 package name appears. (See also <ref id="virtual_pkg">)
4878 If there are both concrete and virtual packages of the same
4879 name, then the dependency may be satisfied (or the conflict
4880 caused) by either the concrete package with the name in
4881 question or any other concrete package which provides the
4882 virtual package with the name in question. This is so that,
4883 for example, supposing we have
4884 <example compact="compact">
4887 </example> and someone else releases an enhanced version of
4888 the <tt>bar</tt> package they can say:
4889 <example compact="compact">
4893 and the <tt>bar-plus</tt> package will now also satisfy the
4894 dependency for the <tt>foo</tt> package.
4898 If a relationship field has a version number attached, only real
4899 packages will be considered to see whether the relationship is
4900 satisfied (or the prohibition violated, for a conflict or
4901 breakage). In other words, if a version number is specified,
4902 this is a request to ignore all <tt>Provides</tt> for that
4903 package name and consider only real packages. The package
4904 manager will assume that a package providing that virtual
4905 package is not of the "right" version. A <tt>Provides</tt>
4906 field may not contain version numbers, and the version number of
4907 the concrete package which provides a particular virtual package
4908 will not be considered when considering a dependency on or
4909 conflict with the virtual package name.<footnote>
4910 It is possible that a future release of <prgn>dpkg</prgn> may
4911 add the ability to specify a version number for each virtual
4912 package it provides. This feature is not yet present,
4913 however, and is expected to be used only infrequently.
4918 To specify which of a set of real packages should be the default
4919 to satisfy a particular dependency on a virtual package, list
4920 the real package as an alternative before the virtual one.
4924 If the virtual package represents a facility that can only be
4925 provided by one real package at a time, such as
4926 the <package>mail-transport-agent</package> virtual package that
4927 requires installation of a binary that would conflict with all
4928 other providers of that virtual package (see
4929 <ref id="mail-transport-agents">), all packages providing that
4930 virtual package should also declare a conflict with it
4931 using <tt>Conflicts</tt>. This will ensure that at most one
4932 provider of that virtual package is unpacked or installed at a
4937 <sect id="replaces"><heading>Overwriting files and replacing
4938 packages - <tt>Replaces</tt></heading>
4941 Packages can declare in their control file that they should
4942 overwrite files in certain other packages, or completely replace
4943 other packages. The <tt>Replaces</tt> control field has these
4944 two distinct purposes.
4947 <sect1><heading>Overwriting files in other packages</heading>
4950 It is usually an error for a package to contain files which
4951 are on the system in another package. However, if the
4952 overwriting package declares that it <tt>Replaces</tt> the one
4953 containing the file being overwritten, then <prgn>dpkg</prgn>
4954 will replace the file from the old package with that from the
4955 new. The file will no longer be listed as "owned" by the old
4956 package and will be taken over by the new package.
4957 Normally, <tt>Breaks</tt> should be used in conjunction
4958 with <tt>Replaces</tt>.<footnote>
4959 To see why <tt>Breaks</tt> is normally needed in addition
4960 to <tt>Replaces</tt>, consider the case of a file in the
4961 package <package>foo</package> being taken over by the
4962 package <package>foo-data</package>.
4963 <tt>Replaces</tt> will allow <package>foo-data</package> to
4964 be installed and take over that file. However,
4965 without <tt>Breaks</tt>, nothing
4966 requires <package>foo</package> to be upgraded to a newer
4967 version that knows it does not include that file and instead
4968 depends on <package>foo-data</package>. Nothing would
4969 prevent the new <package>foo-data</package> package from
4970 being installed and then removed, removing the file that it
4971 took over from <package>foo</package>. After that
4972 operation, the package manager would think the system was in
4973 a consistent state, but the <package>foo</package> package
4974 would be missing one of its files.
4979 For example, if a package <package>foo</package> is split
4980 into <package>foo</package> and <package>foo-data</package>
4981 starting at version 1.2-3, <package>foo-data</package> would
4983 <example compact="compact">
4984 Replaces: foo (<< 1.2-3)
4985 Breaks: foo (<< 1.2-3)
4987 in its control file. The new version of the
4988 package <package>foo</package> would normally have the field
4989 <example compact="compact">
4990 Depends: foo-data (>= 1.2-3)
4992 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4993 the files moved into <package>foo-data</package> are not
4994 required for normal operation).
4998 If a package is completely replaced in this way, so that
4999 <prgn>dpkg</prgn> does not know of any files it still
5000 contains, it is considered to have "disappeared". It will
5001 be marked as not wanted on the system (selected for
5002 removal) and not installed. Any <tt>conffile</tt>s
5003 details noted for the package will be ignored, as they
5004 will have been taken over by the overwriting package. The
5005 package's <prgn>postrm</prgn> script will be run with a
5006 special argument to allow the package to do any final
5007 cleanup required. See <ref id="mscriptsinstact">.
5009 Replaces is a one way relationship. You have to install
5010 the replacing package after the replaced package.
5015 For this usage of <tt>Replaces</tt>, virtual packages (see
5016 <ref id="virtual">) are not considered when looking at a
5017 <tt>Replaces</tt> field. The packages declared as being
5018 replaced must be mentioned by their real names.
5022 This usage of <tt>Replaces</tt> only takes effect when both
5023 packages are at least partially on the system at once. It is
5024 not relevant if the packages conflict unless the conflict has
5029 <sect1><heading>Replacing whole packages, forcing their
5033 Second, <tt>Replaces</tt> allows the packaging system to
5034 resolve which package should be removed when there is a
5035 conflict (see <ref id="conflicts">). This usage only takes
5036 effect when the two packages <em>do</em> conflict, so that the
5037 two usages of this field do not interfere with each other.
5041 In this situation, the package declared as being replaced
5042 can be a virtual package, so for example, all mail
5043 transport agents (MTAs) would have the following fields in
5044 their control files:
5045 <example compact="compact">
5046 Provides: mail-transport-agent
5047 Conflicts: mail-transport-agent
5048 Replaces: mail-transport-agent
5050 ensuring that only one MTA can be installed at any one
5051 time. See <ref id="virtual"> for more information about this
5056 <sect id="sourcebinarydeps">
5057 <heading>Relationships between source and binary packages -
5058 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5059 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5063 Source packages that require certain binary packages to be
5064 installed or absent at the time of building the package
5065 can declare relationships to those binary packages.
5069 This is done using the <tt>Build-Depends</tt>,
5070 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5071 <tt>Build-Conflicts-Indep</tt> control fields.
5075 Build-dependencies on "build-essential" binary packages can be
5076 omitted. Please see <ref id="pkg-relations"> for more information.
5080 The dependencies and conflicts they define must be satisfied
5081 (as defined earlier for binary packages) in order to invoke
5082 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5084 There is no Build-Depends-Arch; this role is essentially
5085 met with Build-Depends. Anyone building the
5086 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5087 assumed to be building the whole package, and therefore
5088 installation of all build dependencies is required.
5091 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5092 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5093 not yet know how to check for its existence, and
5094 <tt>binary-arch</tt>. The purpose of the original split
5095 between <tt>Build-Depends</tt> and
5096 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5097 wouldn't need to install extra packages needed only for the
5098 binary-indep targets. But without a build-arch/build-indep
5099 split, this didn't work, since most of the work is done in
5100 the build target, not in the binary target.
5104 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5105 <tt>binary-arch</tt></tag>
5107 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5108 fields must be satisfied when these targets are invoked.
5110 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5111 and <tt>binary-indep</tt></tag>
5113 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5114 <tt>Build-Depends-Indep</tt>, and
5115 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5116 these targets are invoked.
5124 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5127 Packages containing shared libraries must be constructed with
5128 a little care to make sure that the shared library is always
5129 available. This is especially important for packages whose
5130 shared libraries are vitally important, such as the C library
5131 (currently <tt>libc6</tt>).
5135 This section deals only with public shared libraries: shared
5136 libraries that are placed in directories searched by the dynamic
5137 linker by default or which are intended to be linked against
5138 normally and possibly used by other, independent packages. Shared
5139 libraries that are internal to a particular package or that are
5140 only loaded as dynamic modules are not covered by this section and
5141 are not subject to its requirements.
5145 A shared library is identified by the <tt>SONAME</tt> attribute
5146 stored in its dynamic section. When a binary is linked against a
5147 shared library, the <tt>SONAME</tt> of the shared library is
5148 recorded in the binary's <tt>NEEDED</tt> section so that the
5149 dynamic linker knows that library must be loaded at runtime. The
5150 shared library file's full name (which usually contains additional
5151 version information not needed in the <tt>SONAME</tt>) is
5152 therefore normally not referenced directly. Instead, the shared
5153 library is loaded by its <tt>SONAME</tt>, which exists on the file
5154 system as a symlink pointing to the full name of the shared
5155 library. This symlink must be provided by the
5156 package. <ref id="sharedlibs-runtime"> describes how to do this.
5158 This is a convention of shared library versioning, but not a
5159 requirement. Some libraries use the <tt>SONAME</tt> as the full
5160 library file name instead and therefore do not need a symlink.
5161 Most, however, encode additional information about
5162 backwards-compatible revisions as a minor version number in the
5163 file name. The <tt>SONAME</tt> itself only changes when
5164 binaries linked with the earlier version of the shared library
5165 may no longer work, but the filename may change with each
5166 release of the library. See <ref id="sharedlibs-runtime"> for
5172 When linking a binary or another shared library against a shared
5173 library, the <tt>SONAME</tt> for that shared library is not yet
5174 known. Instead, the shared library is found by looking for a file
5175 matching the library name with <tt>.so</tt> appended. This file
5176 exists on the file system as a symlink pointing to the shared
5181 Shared libraries are normally split into several binary packages.
5182 The <tt>SONAME</tt> symlink is installed by the runtime shared
5183 library package, and the bare <tt>.so</tt> symlink is installed in
5184 the development package since it's only used when linking binaries
5185 or shared libraries. However, there are some exceptions for
5186 unusual shared libraries or for shared libraries that are also
5187 loaded as dynamic modules by other programs.
5191 This section is primarily concerned with how the separation of
5192 shared libraries into multiple packages should be done and how
5193 dependencies on and between shared library binary packages are
5194 managed in Debian. <ref id="libraries"> should be read in
5195 conjunction with this section and contains additional rules for
5196 the files contained in the shared library packages.
5199 <sect id="sharedlibs-runtime">
5200 <heading>Run-time shared libraries</heading>
5203 The run-time shared library must be placed in a package
5204 whose name changes whenever the <tt>SONAME</tt> of the shared
5205 library changes. This allows several versions of the shared
5206 library to be installed at the same time, allowing installation
5207 of the new version of the shared library without immediately
5208 breaking binaries that depend on the old version. Normally, the
5209 run-time shared library and its <tt>SONAME</tt> symlink should
5210 be placed in a package named
5211 <package><var>libraryname</var><var>soversion</var></package>,
5212 where <var>soversion</var> is the version number in
5213 the <tt>SONAME</tt> of the shared library.
5214 See <ref id="shlibs"> for detailed information on how to
5215 determine this version. Alternatively, if it would be confusing
5216 to directly append <var>soversion</var>
5217 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5218 itself ends in a number), you should use
5219 <package><var>libraryname</var>-<var>soversion</var></package>
5224 If you have several shared libraries built from the same source
5225 tree, you may lump them all together into a single shared
5226 library package provided that all of their <tt>SONAME</tt>s will
5227 always change together. Be aware that this is not normally the
5228 case, and if the <tt>SONAME</tt>s do not change together,
5229 upgrading such a merged shared library package will be
5230 unnecessarily difficult because of file conflicts with the old
5231 version of the package. When in doubt, always split shared
5232 library packages so that each binary package installs a single
5237 Every time the shared library ABI changes in a way that may
5238 break binaries linked against older versions of the shared
5239 library, the <tt>SONAME</tt> of the library and the
5240 corresponding name for the binary package containing the runtime
5241 shared library should change. Normally, this means
5242 the <tt>SONAME</tt> should change any time an interface is
5243 removed from the shared library or the signature of an interface
5244 (the number of parameters or the types of parameters that it
5245 takes, for example) is changed. This practice is vital to
5246 allowing clean upgrades from older versions of the package and
5247 clean transitions between the old ABI and new ABI without having
5248 to upgrade every affected package simultaneously.
5252 The <tt>SONAME</tt> and binary package name need not, and indeed
5253 normally should not, change if new interfaces are added but none
5254 are removed or changed, since this will not break binaries
5255 linked against the old shared library. Correct versioning of
5256 dependencies on the newer shared library by binaries that use
5257 the new interfaces is handled via
5258 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5259 system</qref> or via symbols files (see
5260 <manref name="deb-symbols" section="5">).
5264 The package should install the shared libraries under
5265 their normal names. For example, the <package>libgdbm3</package>
5266 package should install <file>libgdbm.so.3.0.0</file> as
5267 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5268 renamed or re-linked by any <prgn>prerm</prgn> or
5269 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5270 of renaming things safely without affecting running programs,
5271 and attempts to interfere with this are likely to lead to
5276 Shared libraries should not be installed executable, since
5277 the dynamic linker does not require this and trying to
5278 execute a shared library usually results in a core dump.
5282 The run-time library package should include the symbolic link for
5283 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5284 the shared libraries. For example,
5285 the <package>libgdbm3</package> package should include a symbolic
5286 link from <file>/usr/lib/libgdbm.so.3</file> to
5287 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5288 linker (for example <prgn>ld.so</prgn> or
5289 <prgn>ld-linux.so.*</prgn>) can find the library between the
5290 time that <prgn>dpkg</prgn> installs it and the time that
5291 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5293 The package management system requires the library to be
5294 placed before the symbolic link pointing to it in the
5295 <file>.deb</file> file. This is so that when
5296 <prgn>dpkg</prgn> comes to install the symlink
5297 (overwriting the previous symlink pointing at an older
5298 version of the library), the new shared library is already
5299 in place. In the past, this was achieved by creating the
5300 library in the temporary packaging directory before
5301 creating the symlink. Unfortunately, this was not always
5302 effective, since the building of the tar file in the
5303 <file>.deb</file> depended on the behavior of the underlying
5304 file system. Some file systems (such as reiserfs) reorder
5305 the files so that the order of creation is forgotten.
5306 Since version 1.7.0, <prgn>dpkg</prgn>
5307 reorders the files itself as necessary when building a
5308 package. Thus it is no longer important to concern
5309 oneself with the order of file creation.
5313 <sect1 id="ldconfig">
5314 <heading><tt>ldconfig</tt></heading>
5317 Any package installing shared libraries in one of the default
5318 library directories of the dynamic linker (which are currently
5319 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5320 listed in <file>/etc/ld.so.conf</file><footnote>
5322 <list compact="compact">
5323 <item>/usr/local/lib</item>
5324 <item>/usr/lib/libc5-compat</item>
5325 <item>/lib/libc5-compat</item>
5328 must use <prgn>ldconfig</prgn> to update the shared library
5333 The package maintainer scripts must only call
5334 <prgn>ldconfig</prgn> under these circumstances:
5335 <list compact="compact">
5336 <item>When the <prgn>postinst</prgn> script is run with a
5337 first argument of <tt>configure</tt>, the script must call
5338 <prgn>ldconfig</prgn>, and may optionally invoke
5339 <prgn>ldconfig</prgn> at other times.
5341 <item>When the <prgn>postrm</prgn> script is run with a
5342 first argument of <tt>remove</tt>, the script should call
5343 <prgn>ldconfig</prgn>.
5348 During install or upgrade, the preinst is called before
5349 the new files are installed, so calling "ldconfig" is
5350 pointless. The preinst of an existing package can also be
5351 called if an upgrade fails. However, this happens during
5352 the critical time when a shared libs may exist on-disk
5353 under a temporary name. Thus, it is dangerous and
5354 forbidden by current policy to call "ldconfig" at this
5359 When a package is installed or upgraded, "postinst
5360 configure" runs after the new files are safely on-disk.
5361 Since it is perfectly safe to invoke ldconfig
5362 unconditionally in a postinst, it is OK for a package to
5363 simply put ldconfig in its postinst without checking the
5364 argument. The postinst can also be called to recover from
5365 a failed upgrade. This happens before any new files are
5366 unpacked, so there is no reason to call "ldconfig" at this
5371 For a package that is being removed, prerm is
5372 called with all the files intact, so calling ldconfig is
5373 useless. The other calls to "prerm" happen in the case of
5374 upgrade at a time when all the files of the old package
5375 are on-disk, so again calling "ldconfig" is pointless.
5379 postrm, on the other hand, is called with the "remove"
5380 argument just after the files are removed, so this is
5381 the proper time to call "ldconfig" to notify the system
5382 of the fact that the shared libraries from the package
5383 are removed. The postrm can be called at several other
5384 times. At the time of "postrm purge", "postrm
5385 abort-install", or "postrm abort-upgrade", calling
5386 "ldconfig" is useless because the shared lib files are
5387 not on-disk. However, when "postrm" is invoked with
5388 arguments "upgrade", "failed-upgrade", or "disappear", a
5389 shared lib may exist on-disk under a temporary filename.
5397 <sect id="sharedlibs-support-files">
5398 <heading>Shared library support files</heading>
5401 If your package contains files whose names do not change with
5402 each change in the library shared object version, you must not
5403 put them in the shared library package. Otherwise, several
5404 versions of the shared library cannot be installed at the same
5405 time without filename clashes, making upgrades and transitions
5406 unnecessarily difficult.
5410 It is recommended that supporting files and run-time support
5411 programs that do not need to be invoked manually by users, but
5412 are nevertheless required for the package to function, be placed
5413 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5414 preferably under <file>/usr/lib/</file><var>package-name</var>.
5415 If the program or file is architecture independent, the
5416 recommendation is for it to be placed in a subdirectory of
5417 <file>/usr/share</file> instead, preferably under
5418 <file>/usr/share/</file><var>package-name</var>. Following the
5419 <var>package-name</var> naming convention ensures that the file
5420 names change when the shared object version changes.
5424 Run-time support programs that use the shared library but are
5425 not required for the library to function or files used by the
5426 shared library that can be used by any version of the shared
5427 library package should instead be put in a separate package.
5428 This package might typically be named
5429 <package><var>libraryname</var>-tools</package>; note the
5430 absence of the <var>soversion</var> in the package name.
5434 Files and support programs only useful when compiling software
5435 against the library should be included in the development
5436 package for the library.<footnote>
5437 For example, a <file><var>package-name</var>-config</file>
5438 script or <package>pkg-config</package> configuration files.
5443 <sect id="sharedlibs-static">
5444 <heading>Static libraries</heading>
5447 The static library (<file><var>libraryname.a</var></file>)
5448 is usually provided in addition to the shared version.
5449 It is placed into the development package (see below).
5453 In some cases, it is acceptable for a library to be
5454 available in static form only; these cases include:
5456 <item>libraries for languages whose shared library support
5457 is immature or unstable</item>
5458 <item>libraries whose interfaces are in flux or under
5459 development (commonly the case when the library's
5460 major version number is zero, or where the ABI breaks
5461 across patchlevels)</item>
5462 <item>libraries which are explicitly intended to be
5463 available only in static form by their upstream
5468 <sect id="sharedlibs-dev">
5469 <heading>Development files</heading>
5472 If there are development files associated with a shared library,
5473 the source package needs to generate a binary development package
5474 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5475 or if you prefer only to support one development version at a
5476 time, <package><var>libraryname</var>-dev</package>. Installing
5477 the development package must result in installation of all the
5478 development files necessary for compiling programs against that
5479 shared library.<footnote>
5480 This wording allows the development files to be split into
5481 several packages, such as a separate architecture-independent
5482 <package><var>libraryname</var>-headers</package>, provided that
5483 the development package depends on all the required additional
5489 In case several development versions of a library exist, you may
5490 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5491 <ref id="conflicts">) to ensure that the user only installs one
5492 development version at a time (as different development versions are
5493 likely to have the same header files in them, which would cause a
5494 filename clash if both were installed).
5498 The development package should contain a symlink for the associated
5499 shared library without a version number. For example, the
5500 <package>libgdbm-dev</package> package should include a symlink
5501 from <file>/usr/lib/libgdbm.so</file> to
5502 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5503 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5504 <file>libgdbm.so</file> when compiling dynamically.
5508 If the package provides Ada Library Information
5509 (<file>*.ali</file>) files for use with GNAT, these files must be
5510 installed read-only (mode 0444) so that GNAT will not attempt to
5511 recompile them. This overrides the normal file mode requirements
5512 given in <ref id="permissions-owners">.
5516 <sect id="sharedlibs-intradeps">
5517 <heading>Dependencies between the packages of the same library</heading>
5520 Typically the development version should have an exact
5521 version dependency on the runtime library, to make sure that
5522 compilation and linking happens correctly. The
5523 <tt>${binary:Version}</tt> substitution variable can be
5524 useful for this purpose.
5526 Previously, <tt>${Source-Version}</tt> was used, but its name
5527 was confusing and it has been deprecated since dpkg 1.13.19.
5532 <sect id="sharedlibs-shlibdeps">
5533 <heading>Dependencies between the library and other packages -
5534 the <tt>shlibs</tt> system</heading>
5537 If a package contains a binary or library which links to a
5538 shared library, we must ensure that when the package is
5539 installed on the system, all of the libraries needed are
5540 also installed. This requirement led to the creation of the
5541 <tt>shlibs</tt> system, which is very simple in its design:
5542 any package which <em>provides</em> a shared library also
5543 provides information on the package dependencies required to
5544 ensure the presence of this library, and any package which
5545 <em>uses</em> a shared library uses this information to
5546 determine the dependencies it requires. The files which
5547 contain the mapping from shared libraries to the necessary
5548 dependency information are called <file>shlibs</file> files.
5552 When a package is built which contains any shared libraries, it
5553 must provide a <file>shlibs</file> file for other packages to
5554 use. When a package is built which contains any shared
5555 libraries or compiled binaries, it must run
5556 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5557 on these to determine the libraries used and hence the
5558 dependencies needed by this package.<footnote>
5560 <prgn>dpkg-shlibdeps</prgn> will use a program
5561 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5562 the libraries directly needed by the binaries or shared
5563 libraries in the package.
5567 We say that a binary <tt>foo</tt> <em>directly</em> uses
5568 a library <tt>libbar</tt> if it is explicitly linked
5569 with that library (that is, the library is listed in the ELF
5570 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5571 to the link line when the binary is created). Other
5572 libraries that are needed by <tt>libbar</tt> are linked
5573 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5574 linker will load them automatically when it loads
5575 <tt>libbar</tt>. A package should depend on the libraries
5576 it directly uses, but not the libraries it indirectly uses.
5577 The dependencies for those libraries will automatically pull
5578 in the other libraries.
5582 A good example of where this helps is the following. We
5583 could update <tt>libimlib</tt> with a new version that
5584 supports a new graphics format called dgf (but retaining the
5585 same major version number) and depends on <tt>libdgf</tt>.
5586 If we used <prgn>ldd</prgn> to add dependencies for every
5587 library directly or indirectly linked with a binary, every
5588 package that uses <tt>libimlib</tt> would need to be
5589 recompiled so it would also depend on <tt>libdgf</tt> or it
5590 wouldn't run due to missing symbols. Since dependencies are
5591 only added based on ELF <tt>NEEDED</tt> attribute, packages
5592 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5593 having the dependency on <tt>libdgf</tt> and so they would
5594 not need rebuilding.
5600 In the following sections, we will first describe where the
5601 various <tt>shlibs</tt> files are to be found, then how to
5602 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5603 file format and how to create them if your package contains a
5608 <heading>The <tt>shlibs</tt> files present on the system</heading>
5611 There are several places where <tt>shlibs</tt> files are
5612 found. The following list gives them in the order in which
5614 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5615 (The first one which gives the required information is used.)
5621 <p><file>debian/shlibs.local</file></p>
5624 This lists overrides for this package. This file should
5625 normally not be used, but may be needed temporarily in
5626 unusual situations to work around bugs in other packages,
5627 or in unusual cases where the normally declared dependency
5628 information in the installed <file>shlibs</file> file for
5629 a library cannot be used. This file overrides information
5630 obtained from any other source.
5635 <p><file>/etc/dpkg/shlibs.override</file></p>
5638 This lists global overrides. This list is normally
5639 empty. It is maintained by the local system
5645 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5648 When packages are being built,
5649 any <file>debian/shlibs</file> files are copied into the
5650 control information file area of the temporary build
5651 directory and given the name <file>shlibs</file>. These
5652 files give details of any shared libraries included in the
5653 same package.<footnote>
5654 An example may help here. Let us say that the source
5655 package <tt>foo</tt> generates two binary
5656 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5657 When building the binary packages, the two packages are
5658 created in the directories <file>debian/libfoo2</file>
5659 and <file>debian/foo-runtime</file> respectively.
5660 (<file>debian/tmp</file> could be used instead of one of
5661 these.) Since <tt>libfoo2</tt> provides the
5662 <tt>libfoo</tt> shared library, it will require a
5663 <tt>shlibs</tt> file, which will be installed in
5664 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5665 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5666 When <prgn>dpkg-shlibdeps</prgn> is run on the
5667 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5669 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5670 determine whether <tt>foo-prog</tt>'s library
5671 dependencies are satisfied by any of the libraries
5672 provided by <tt>libfoo2</tt>. For this reason,
5673 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5674 the individual binary packages' <tt>shlibs</tt> files
5675 have been installed into the build directory.
5681 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5684 These are the <file>shlibs</file> files corresponding to
5685 all of the packages installed on the system, and are
5686 maintained by the relevant package maintainers.
5691 <p><file>/etc/dpkg/shlibs.default</file></p>
5694 This file lists any shared libraries whose packages
5695 have failed to provide correct <file>shlibs</file> files.
5696 It was used when the <file>shlibs</file> setup was first
5697 introduced, but it is now normally empty. It is
5698 maintained by the <tt>dpkg</tt> maintainer.
5706 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5707 <file>shlibs</file> files</heading>
5711 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5712 into your <file>debian/rules</file> file. If your package
5713 contains only compiled binaries and libraries (but no scripts),
5714 you can use a command such as:
5715 <example compact="compact">
5716 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5717 debian/tmp/usr/lib/*
5719 Otherwise, you will need to explicitly list the compiled
5720 binaries and libraries.<footnote>
5721 If you are using <tt>debhelper</tt>, the
5722 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5723 It will also correctly handle multi-binary packages.
5728 This command puts the dependency information into the
5729 <file>debian/substvars</file> file, which is then used by
5730 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5731 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5732 field in the control file for this to work.
5736 If you have multiple binary packages, you will need to call
5737 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5738 compiled libraries or binaries. In such a case, you will
5739 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5740 utilities to specify a different <file>substvars</file> file.
5744 If you are creating a udeb for use in the Debian Installer,
5745 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5746 should use the dependency line of type <tt>udeb</tt> by
5747 adding the <tt>-tudeb</tt> option<footnote>
5748 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5749 will automatically add this option if it knows it is
5751 </footnote>. If there is no dependency line of
5752 type <tt>udeb</tt> in the <file>shlibs</file>
5753 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5758 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5759 <ref id="pkg-dpkg-shlibdeps"> and
5760 <manref name="dpkg-shlibdeps" section="1">.
5765 <heading>The <file>shlibs</file> File Format</heading>
5768 Each <file>shlibs</file> file has the same format. Lines
5769 beginning with <tt>#</tt> are considered to be comments and
5770 are ignored. Each line is of the form:
5771 <example compact="compact">
5772 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5777 We will explain this by reference to the example of the
5778 <tt>zlib1g</tt> package, which (at the time of writing)
5779 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5783 <var>type</var> is an optional element that indicates the type
5784 of package for which the line is valid. The only type currently
5785 in use is <tt>udeb</tt>. The colon and space after the type are
5790 <var>library-name</var> is the name of the shared library,
5791 in this case <tt>libz</tt>. (This must match the name part
5792 of the soname, see below.)
5796 <var>soname-version</var> is the version part of the soname of
5797 the library. The soname is the thing that must exactly match
5798 for the library to be recognized by the dynamic linker, and is
5800 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5801 example, <tt>libz.so.1</tt>.<footnote>
5802 This can be determined using the command
5803 <example compact="compact">
5804 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5807 The version part is the part which comes after
5808 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5809 instead be of the form
5810 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5811 as <tt>libdb-4.8.so</tt>, in which case the name would
5812 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5816 <var>dependencies</var> has the same syntax as a dependency
5817 field in a binary package control file. It should give
5818 details of which packages are required to satisfy a binary
5819 built against the version of the library contained in the
5820 package. See <ref id="depsyntax"> for details.
5824 In our example, if the first version of the <tt>zlib1g</tt>
5825 package which contained a minor number of at least
5826 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5827 <tt>shlibs</tt> entry for this library could say:
5828 <example compact="compact">
5829 libz 1 zlib1g (>= 1:1.1.3)
5831 The version-specific dependency is to avoid warnings from
5832 the dynamic linker about using older shared libraries with
5837 As zlib1g also provides a udeb containing the shared library,
5838 there would also be a second line:
5839 <example compact="compact">
5840 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5846 <heading>Providing a <file>shlibs</file> file</heading>
5849 If your package provides a shared library, you need to create
5850 a <file>shlibs</file> file following the format described above.
5851 It is usual to call this file <file>debian/shlibs</file> (but if
5852 you have multiple binary packages, you might want to call it
5853 <file>debian/shlibs.<var>package</var></file> instead). Then
5854 let <file>debian/rules</file> install it in the control
5855 information file area:
5856 <example compact="compact">
5857 install -m644 debian/shlibs debian/tmp/DEBIAN
5859 or, in the case of a multi-binary package:
5860 <example compact="compact">
5861 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5863 An alternative way of doing this is to create the
5864 <file>shlibs</file> file in the control information file area
5865 directly from <file>debian/rules</file> without using
5866 a <file>debian/shlibs</file> file at all,<footnote>
5867 This is what <prgn>dh_makeshlibs</prgn> in
5868 the <package>debhelper</package> suite does. If your package
5869 also has a udeb that provides a shared
5870 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5871 the <tt>udeb:</tt> lines if you specify the name of the udeb
5872 with the <tt>--add-udeb</tt> option.
5874 since the <file>debian/shlibs</file> file itself is ignored by
5875 <prgn>dpkg-shlibdeps</prgn>.
5879 As <prgn>dpkg-shlibdeps</prgn> reads the
5880 <file>DEBIAN/shlibs</file> files in all of the binary packages
5881 being built from this source package, all of the
5882 <file>DEBIAN/shlibs</file> files should be installed before
5883 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5891 <chapt id="opersys"><heading>The Operating System</heading>
5894 <heading>File system hierarchy</heading>
5898 <heading>File System Structure</heading>
5901 The location of all installed files and directories must
5902 comply with the Filesystem Hierarchy Standard (FHS),
5903 version 2.3, with the exceptions noted below, and except
5904 where doing so would violate other terms of Debian
5905 Policy. The following exceptions to the FHS apply:
5910 The optional rules related to user specific
5911 configuration files for applications are stored in
5912 the user's home directory are relaxed. It is
5913 recommended that such files start with the
5914 '<tt>.</tt>' character (a "dot file"), and if an
5915 application needs to create more than one dot file
5916 then the preferred placement is in a subdirectory
5917 with a name starting with a '.' character, (a "dot
5918 directory"). In this case it is recommended the
5919 configuration files not start with the '.'
5925 The requirement for amd64 to use <file>/lib64</file>
5926 for 64 bit binaries is removed.
5931 The requirement for object files, internal binaries, and
5932 libraries, including <file>libc.so.*</file>, to be located
5933 directly under <file>/lib{,32}</file> and
5934 <file>/usr/lib{,32}</file> is amended, permitting files
5935 to instead be installed to
5936 <file>/lib/<var>triplet</var></file> and
5937 <file>/usr/lib/<var>triplet</var></file>, where
5938 <tt><var>triplet</var></tt> is the value returned by
5939 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5940 architecture of the package. Packages may <em>not</em>
5941 install files to any <var>triplet</var> path other
5942 than the one matching the architecture of that package;
5943 for instance, an <tt>Architecture: amd64</tt> package
5944 containing 32-bit x86 libraries may not install these
5945 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5947 This is necessary in order to reserve the directories for
5948 use in cross-installation of library packages from other
5949 architectures, as part of the planned deployment of
5954 Applications may also use a single subdirectory under
5955 <file>/usr/lib/<var>triplet</var></file>.
5958 The execution time linker/loader, ld*, must still be made
5959 available in the existing location under /lib or /lib64
5960 since this is part of the ELF ABI for the architecture.
5965 The requirement that
5966 <file>/usr/local/share/man</file> be "synonymous"
5967 with <file>/usr/local/man</file> is relaxed to a
5972 The requirement that windowmanagers with a single
5973 configuration file call it <file>system.*wmrc</file>
5974 is removed, as is the restriction that the window
5975 manager subdirectory be named identically to the
5976 window manager name itself.
5981 The requirement that boot manager configuration
5982 files live in <file>/etc</file>, or at least are
5983 symlinked there, is relaxed to a recommendation.
5988 The following directories in the root filesystem are
5989 additionally allowed: <file>/sys</file> and
5990 <file>/selinux</file>. <footnote>These directories
5991 are used as mount points to mount virtual filesystems
5992 to get access to kernel information.</footnote>
5999 The version of this document referred here can be
6000 found in the <tt>debian-policy</tt> package or on <url
6001 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6002 name="FHS (Debian copy)"> alongside this manual (or, if
6003 you have the <package>debian-policy</package> installed,
6005 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6006 (local copy)">). The
6007 latest version, which may be a more recent version, may
6009 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6010 Specific questions about following the standard may be
6011 asked on the <tt>debian-devel</tt> mailing list, or
6012 referred to the FHS mailing list (see the
6013 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6019 <heading>Site-specific programs</heading>
6022 As mandated by the FHS, packages must not place any
6023 files in <file>/usr/local</file>, either by putting them in
6024 the file system archive to be unpacked by <prgn>dpkg</prgn>
6025 or by manipulating them in their maintainer scripts.
6029 However, the package may create empty directories below
6030 <file>/usr/local</file> so that the system administrator knows
6031 where to place site-specific files. These are not
6032 directories <em>in</em> <file>/usr/local</file>, but are
6033 children of directories in <file>/usr/local</file>. These
6034 directories (<file>/usr/local/*/dir/</file>)
6035 should be removed on package removal if they are
6040 Note that this applies only to
6041 directories <em>below</em> <file>/usr/local</file>,
6042 not <em>in</em> <file>/usr/local</file>. Packages must
6043 not create sub-directories in the
6044 directory <file>/usr/local</file> itself, except those
6045 listed in FHS, section 4.5. However, you may create
6046 directories below them as you wish. You must not remove
6047 any of the directories listed in 4.5, even if you created
6052 Since <file>/usr/local</file> can be mounted read-only from a
6053 remote server, these directories must be created and
6054 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6055 maintainer scripts and not be included in the
6056 <file>.deb</file> archive. These scripts must not fail if
6057 either of these operations fail.
6061 For example, the <tt>emacsen-common</tt> package could
6062 contain something like
6063 <example compact="compact">
6064 if [ ! -e /usr/local/share/emacs ]
6066 if mkdir /usr/local/share/emacs 2>/dev/null
6068 chown root:staff /usr/local/share/emacs
6069 chmod 2775 /usr/local/share/emacs
6073 in its <prgn>postinst</prgn> script, and
6074 <example compact="compact">
6075 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6076 rmdir /usr/local/share/emacs 2>/dev/null || true
6078 in the <prgn>prerm</prgn> script. (Note that this form is
6079 used to ensure that if the script is interrupted, the
6080 directory <file>/usr/local/share/emacs</file> will still be
6085 If you do create a directory in <file>/usr/local</file> for
6086 local additions to a package, you should ensure that
6087 settings in <file>/usr/local</file> take precedence over the
6088 equivalents in <file>/usr</file>.
6092 However, because <file>/usr/local</file> and its contents are
6093 for exclusive use of the local administrator, a package
6094 must not rely on the presence or absence of files or
6095 directories in <file>/usr/local</file> for normal operation.
6099 The <file>/usr/local</file> directory itself and all the
6100 subdirectories created by the package should (by default) have
6101 permissions 2775 (group-writable and set-group-id) and be
6102 owned by <tt>root:staff</tt>.
6107 <heading>The system-wide mail directory</heading>
6109 The system-wide mail directory
6110 is <file>/var/mail</file>. This directory is part of the
6111 base system and should not be owned by any particular mail
6112 agents. The use of the old
6113 location <file>/var/spool/mail</file> is deprecated, even
6114 though the spool may still be physically located there.
6120 <heading>Users and groups</heading>
6123 <heading>Introduction</heading>
6125 The Debian system can be configured to use either plain or
6130 Some user ids (UIDs) and group ids (GIDs) are reserved
6131 globally for use by certain packages. Because some
6132 packages need to include files which are owned by these
6133 users or groups, or need the ids compiled into binaries,
6134 these ids must be used on any Debian system only for the
6135 purpose for which they are allocated. This is a serious
6136 restriction, and we should avoid getting in the way of
6137 local administration policies. In particular, many sites
6138 allocate users and/or local system groups starting at 100.
6142 Apart from this we should have dynamically allocated ids,
6143 which should by default be arranged in some sensible
6144 order, but the behavior should be configurable.
6148 Packages other than <tt>base-passwd</tt> must not modify
6149 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6150 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6155 <heading>UID and GID classes</heading>
6157 The UID and GID numbers are divided into classes as
6163 Globally allocated by the Debian project, the same
6164 on every Debian system. These ids will appear in
6165 the <file>passwd</file> and <file>group</file> files of all
6166 Debian systems, new ids in this range being added
6167 automatically as the <tt>base-passwd</tt> package is
6172 Packages which need a single statically allocated
6173 uid or gid should use one of these; their
6174 maintainers should ask the <tt>base-passwd</tt>
6182 Dynamically allocated system users and groups.
6183 Packages which need a user or group, but can have
6184 this user or group allocated dynamically and
6185 differently on each system, should use <tt>adduser
6186 --system</tt> to create the group and/or user.
6187 <prgn>adduser</prgn> will check for the existence of
6188 the user or group, and if necessary choose an unused
6189 id based on the ranges specified in
6190 <file>adduser.conf</file>.
6194 <tag>1000-59999:</tag>
6197 Dynamically allocated user accounts. By default
6198 <prgn>adduser</prgn> will choose UIDs and GIDs for
6199 user accounts in this range, though
6200 <file>adduser.conf</file> may be used to modify this
6205 <tag>60000-64999:</tag>
6208 Globally allocated by the Debian project, but only
6209 created on demand. The ids are allocated centrally
6210 and statically, but the actual accounts are only
6211 created on users' systems on demand.
6215 These ids are for packages which are obscure or
6216 which require many statically-allocated ids. These
6217 packages should check for and create the accounts in
6218 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6219 <prgn>adduser</prgn> if it has this facility) if
6220 necessary. Packages which are likely to require
6221 further allocations should have a "hole" left after
6222 them in the allocation, to give them room to
6227 <tag>65000-65533:</tag>
6235 User <tt>nobody</tt>. The corresponding gid refers
6236 to the group <tt>nogroup</tt>.
6243 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6244 not</em> be used, because it is the error return
6253 <sect id="sysvinit">
6254 <heading>System run levels and <file>init.d</file> scripts</heading>
6256 <sect1 id="/etc/init.d">
6257 <heading>Introduction</heading>
6260 The <file>/etc/init.d</file> directory contains the scripts
6261 executed by <prgn>init</prgn> at boot time and when the
6262 init state (or "runlevel") is changed (see <manref
6263 name="init" section="8">).
6267 There are at least two different, yet functionally
6268 equivalent, ways of handling these scripts. For the sake
6269 of simplicity, this document describes only the symbolic
6270 link method. However, it must not be assumed by maintainer
6271 scripts that this method is being used, and any automated
6272 manipulation of the various runlevel behaviors by
6273 maintainer scripts must be performed using
6274 <prgn>update-rc.d</prgn> as described below and not by
6275 manually installing or removing symlinks. For information
6276 on the implementation details of the other method,
6277 implemented in the <tt>file-rc</tt> package, please refer
6278 to the documentation of that package.
6282 These scripts are referenced by symbolic links in the
6283 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6284 runlevels, <prgn>init</prgn> looks in the directory
6285 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6286 execute, where <tt><var>n</var></tt> is the runlevel that
6287 is being changed to, or <tt>S</tt> for the boot-up
6292 The names of the links all have the form
6293 <file>S<var>mm</var><var>script</var></file> or
6294 <file>K<var>mm</var><var>script</var></file> where
6295 <var>mm</var> is a two-digit number and <var>script</var>
6296 is the name of the script (this should be the same as the
6297 name of the actual script in <file>/etc/init.d</file>).
6301 When <prgn>init</prgn> changes runlevel first the targets
6302 of the links whose names start with a <tt>K</tt> are
6303 executed, each with the single argument <tt>stop</tt>,
6304 followed by the scripts prefixed with an <tt>S</tt>, each
6305 with the single argument <tt>start</tt>. (The links are
6306 those in the <file>/etc/rc<var>n</var>.d</file> directory
6307 corresponding to the new runlevel.) The <tt>K</tt> links
6308 are responsible for killing services and the <tt>S</tt>
6309 link for starting services upon entering the runlevel.
6313 For example, if we are changing from runlevel 2 to
6314 runlevel 3, init will first execute all of the <tt>K</tt>
6315 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6316 all of the <tt>S</tt> prefixed scripts in that directory.
6317 The links starting with <tt>K</tt> will cause the
6318 referred-to file to be executed with an argument of
6319 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6324 The two-digit number <var>mm</var> is used to determine
6325 the order in which to run the scripts: low-numbered links
6326 have their scripts run first. For example, the
6327 <tt>K20</tt> scripts will be executed before the
6328 <tt>K30</tt> scripts. This is used when a certain service
6329 must be started before another. For example, the name
6330 server <prgn>bind</prgn> might need to be started before
6331 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6332 can set up its access lists. In this case, the script
6333 that starts <prgn>bind</prgn> would have a lower number
6334 than the script that starts <prgn>inn</prgn> so that it
6336 <example compact="compact">
6343 The two runlevels 0 (halt) and 6 (reboot) are slightly
6344 different. In these runlevels, the links with an
6345 <tt>S</tt> prefix are still called after those with a
6346 <tt>K</tt> prefix, but they too are called with the single
6347 argument <tt>stop</tt>.
6351 <sect1 id="writing-init">
6352 <heading>Writing the scripts</heading>
6355 Packages that include daemons for system services should
6356 place scripts in <file>/etc/init.d</file> to start or stop
6357 services at boot time or during a change of runlevel.
6358 These scripts should be named
6359 <file>/etc/init.d/<var>package</var></file>, and they should
6360 accept one argument, saying what to do:
6363 <tag><tt>start</tt></tag>
6364 <item>start the service,</item>
6366 <tag><tt>stop</tt></tag>
6367 <item>stop the service,</item>
6369 <tag><tt>restart</tt></tag>
6370 <item>stop and restart the service if it's already running,
6371 otherwise start the service</item>
6373 <tag><tt>reload</tt></tag>
6374 <item><p>cause the configuration of the service to be
6375 reloaded without actually stopping and restarting
6378 <tag><tt>force-reload</tt></tag>
6379 <item>cause the configuration to be reloaded if the
6380 service supports this, otherwise restart the
6384 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6385 <tt>force-reload</tt> options should be supported by all
6386 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6391 The <file>init.d</file> scripts must ensure that they will
6392 behave sensibly (i.e., returning success and not starting
6393 multiple copies of a service) if invoked with <tt>start</tt>
6394 when the service is already running, or with <tt>stop</tt>
6395 when it isn't, and that they don't kill unfortunately-named
6396 user processes. The best way to achieve this is usually to
6397 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6402 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6403 scripts. Writing correct <file>init.d</file> scripts requires
6404 accepting various error exit statuses when daemons are already
6405 running or already stopped without aborting
6406 the <file>init.d</file> script, and common <file>init.d</file>
6407 function libraries are not safe to call with <tt>set -e</tt>
6409 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6410 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6411 in effect and echoing status messages to the console fails,
6413 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6414 to not use <tt>set -e</tt> and instead check the result of
6415 each command separately.
6419 If a service reloads its configuration automatically (as
6420 in the case of <prgn>cron</prgn>, for example), the
6421 <tt>reload</tt> option of the <file>init.d</file> script
6422 should behave as if the configuration has been reloaded
6427 The <file>/etc/init.d</file> scripts must be treated as
6428 configuration files, either (if they are present in the
6429 package, that is, in the .deb file) by marking them as
6430 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6431 by managing them correctly in the maintainer scripts (see
6432 <ref id="config-files">). This is important since we want
6433 to give the local system administrator the chance to adapt
6434 the scripts to the local system, e.g., to disable a
6435 service without de-installing the package, or to specify
6436 some special command line options when starting a service,
6437 while making sure their changes aren't lost during the next
6442 These scripts should not fail obscurely when the
6443 configuration files remain but the package has been
6444 removed, as configuration files remain on the system after
6445 the package has been removed. Only when <prgn>dpkg</prgn>
6446 is executed with the <tt>--purge</tt> option will
6447 configuration files be removed. In particular, as the
6448 <file>/etc/init.d/<var>package</var></file> script itself is
6449 usually a <tt>conffile</tt>, it will remain on the system
6450 if the package is removed but not purged. Therefore, you
6451 should include a <tt>test</tt> statement at the top of the
6453 <example compact="compact">
6454 test -f <var>program-executed-later-in-script</var> || exit 0
6459 Often there are some variables in the <file>init.d</file>
6460 scripts whose values control the behavior of the scripts,
6461 and which a system administrator is likely to want to
6462 change. As the scripts themselves are frequently
6463 <tt>conffile</tt>s, modifying them requires that the
6464 administrator merge in their changes each time the package
6465 is upgraded and the <tt>conffile</tt> changes. To ease
6466 the burden on the system administrator, such configurable
6467 values should not be placed directly in the script.
6468 Instead, they should be placed in a file in
6469 <file>/etc/default</file>, which typically will have the same
6470 base name as the <file>init.d</file> script. This extra file
6471 should be sourced by the script when the script runs. It
6472 must contain only variable settings and comments in SUSv3
6473 <prgn>sh</prgn> format. It may either be a
6474 <tt>conffile</tt> or a configuration file maintained by
6475 the package maintainer scripts. See <ref id="config-files">
6480 To ensure that vital configurable values are always
6481 available, the <file>init.d</file> script should set default
6482 values for each of the shell variables it uses, either
6483 before sourcing the <file>/etc/default/</file> file or
6484 afterwards using something like the <tt>:
6485 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6486 script must behave sensibly and not fail if the
6487 <file>/etc/default</file> file is deleted.
6491 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6492 as temporary filesystems<footnote>
6493 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6494 options in <file>/etc/default/rcS</file>.
6495 </footnote>, so the <file>init.d</file> scripts must handle this
6496 correctly. This will typically amount to creating any required
6497 subdirectories dynamically when the <file>init.d</file> script
6498 is run, rather than including them in the package and relying on
6499 <prgn>dpkg</prgn> to create them.
6504 <heading>Interfacing with the initscript system</heading>
6507 Maintainers should use the abstraction layer provided by
6508 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6509 programs to deal with initscripts in their packages'
6510 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6511 and <prgn>postrm</prgn>.
6515 Directly managing the /etc/rc?.d links and directly
6516 invoking the <file>/etc/init.d/</file> initscripts should
6517 be done only by packages providing the initscript
6518 subsystem (such as <prgn>sysv-rc</prgn> and
6519 <prgn>file-rc</prgn>).
6523 <heading>Managing the links</heading>
6526 The program <prgn>update-rc.d</prgn> is provided for
6527 package maintainers to arrange for the proper creation and
6528 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6529 or their functional equivalent if another method is being
6530 used. This may be used by maintainers in their packages'
6531 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6535 You must not include any <file>/etc/rc<var>n</var>.d</file>
6536 symbolic links in the actual archive or manually create or
6537 remove the symbolic links in maintainer scripts; you must
6538 use the <prgn>update-rc.d</prgn> program instead. (The
6539 former will fail if an alternative method of maintaining
6540 runlevel information is being used.) You must not include
6541 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6542 in the archive either. (Only the <tt>sysvinit</tt>
6547 By default <prgn>update-rc.d</prgn> will start services in
6548 each of the multi-user state runlevels (2, 3, 4, and 5)
6549 and stop them in the halt runlevel (0), the single-user
6550 runlevel (1) and the reboot runlevel (6). The system
6551 administrator will have the opportunity to customize
6552 runlevels by simply adding, moving, or removing the
6553 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6554 symbolic links are being used, or by modifying
6555 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6560 To get the default behavior for your package, put in your
6561 <prgn>postinst</prgn> script
6562 <example compact="compact">
6563 update-rc.d <var>package</var> defaults
6565 and in your <prgn>postrm</prgn>
6566 <example compact="compact">
6567 if [ "$1" = purge ]; then
6568 update-rc.d <var>package</var> remove
6570 </example>. Note that if your package changes runlevels
6571 or priority, you may have to remove and recreate the links,
6572 since otherwise the old links may persist. Refer to the
6573 documentation of <prgn>update-rc.d</prgn>.
6577 This will use a default sequence number of 20. If it does
6578 not matter when or in which order the <file>init.d</file>
6579 script is run, use this default. If it does, then you
6580 should talk to the maintainer of the <prgn>sysvinit</prgn>
6581 package or post to <tt>debian-devel</tt>, and they will
6582 help you choose a number.
6586 For more information about using <tt>update-rc.d</tt>,
6587 please consult its man page <manref name="update-rc.d"
6593 <heading>Running initscripts</heading>
6595 The program <prgn>invoke-rc.d</prgn> is provided to make
6596 it easier for package maintainers to properly invoke an
6597 initscript, obeying runlevel and other locally-defined
6598 constraints that might limit a package's right to start,
6599 stop and otherwise manage services. This program may be
6600 used by maintainers in their packages' scripts.
6604 The package maintainer scripts must use
6605 <prgn>invoke-rc.d</prgn> to invoke the
6606 <file>/etc/init.d/*</file> initscripts, instead of
6607 calling them directly.
6611 By default, <prgn>invoke-rc.d</prgn> will pass any
6612 action requests (start, stop, reload, restart...) to the
6613 <file>/etc/init.d</file> script, filtering out requests
6614 to start or restart a service out of its intended
6619 Most packages will simply need to change:
6620 <example compact="compact">/etc/init.d/<package>
6621 <action></example> in their <prgn>postinst</prgn>
6622 and <prgn>prerm</prgn> scripts to:
6623 <example compact="compact">
6624 if which invoke-rc.d >/dev/null 2>&1; then
6625 invoke-rc.d <var>package</var> <action>
6627 /etc/init.d/<var>package</var> <action>
6633 A package should register its initscript services using
6634 <prgn>update-rc.d</prgn> before it tries to invoke them
6635 using <prgn>invoke-rc.d</prgn>. Invocation of
6636 unregistered services may fail.
6640 For more information about using
6641 <prgn>invoke-rc.d</prgn>, please consult its man page
6642 <manref name="invoke-rc.d" section="8">.
6648 <heading>Boot-time initialization</heading>
6651 There used to be another directory, <file>/etc/rc.boot</file>,
6652 which contained scripts which were run once per machine
6653 boot. This has been deprecated in favour of links from
6654 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6655 described in <ref id="/etc/init.d">. Packages must not
6656 place files in <file>/etc/rc.boot</file>.
6661 <heading>Example</heading>
6664 An example on which you can base your
6665 <file>/etc/init.d</file> scripts is found in
6666 <file>/etc/init.d/skeleton</file>.
6673 <heading>Console messages from <file>init.d</file> scripts</heading>
6676 This section describes the formats to be used for messages
6677 written to standard output by the <file>/etc/init.d</file>
6678 scripts. The intent is to improve the consistency of
6679 Debian's startup and shutdown look and feel. For this
6680 reason, please look very carefully at the details. We want
6681 the messages to have the same format in terms of wording,
6682 spaces, punctuation and case of letters.
6686 Here is a list of overall rules that should be used for
6687 messages generated by <file>/etc/init.d</file> scripts.
6693 The message should fit in one line (fewer than 80
6694 characters), start with a capital letter and end with
6695 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6699 If the script is performing some time consuming task in
6700 the background (not merely starting or stopping a
6701 program, for instance), an ellipsis (three dots:
6702 <tt>...</tt>) should be output to the screen, with no
6703 leading or tailing whitespace or line feeds.
6707 The messages should appear as if the computer is telling
6708 the user what it is doing (politely :-), but should not
6709 mention "it" directly. For example, instead of:
6710 <example compact="compact">
6711 I'm starting network daemons: nfsd mountd.
6713 the message should say
6714 <example compact="compact">
6715 Starting network daemons: nfsd mountd.
6722 <tt>init.d</tt> script should use the following standard
6723 message formats for the situations enumerated below.
6729 <p>When daemons are started</p>
6732 If the script starts one or more daemons, the output
6733 should look like this (a single line, no leading
6735 <example compact="compact">
6736 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6738 The <var>description</var> should describe the
6739 subsystem the daemon or set of daemons are part of,
6740 while <var>daemon-1</var> up to <var>daemon-n</var>
6741 denote each daemon's name (typically the file name of
6746 For example, the output of <file>/etc/init.d/lpd</file>
6748 <example compact="compact">
6749 Starting printer spooler: lpd.
6754 This can be achieved by saying
6755 <example compact="compact">
6756 echo -n "Starting printer spooler: lpd"
6757 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6760 in the script. If there are more than one daemon to
6761 start, the output should look like this:
6762 <example compact="compact">
6763 echo -n "Starting remote file system services:"
6764 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6765 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6766 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6769 This makes it possible for the user to see what is
6770 happening and when the final daemon has been started.
6771 Care should be taken in the placement of white spaces:
6772 in the example above the system administrators can
6773 easily comment out a line if they don't want to start
6774 a specific daemon, while the displayed message still
6780 <p>When a system parameter is being set</p>
6783 If you have to set up different system parameters
6784 during the system boot, you should use this format:
6785 <example compact="compact">
6786 Setting <var>parameter</var> to "<var>value</var>".
6791 You can use a statement such as the following to get
6793 <example compact="compact">
6794 echo "Setting DNS domainname to \"$domainname\"."
6799 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6800 for the left and right quotation marks. A grave accent
6801 (<tt>`</tt>) is not a quote character; neither is an
6802 apostrophe (<tt>'</tt>).
6807 <p>When a daemon is stopped or restarted</p>
6810 When you stop or restart a daemon, you should issue a
6811 message identical to the startup message, except that
6812 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6813 or <tt>Restarting</tt> respectively.
6817 For example, stopping the printer daemon will look like
6819 <example compact="compact">
6820 Stopping printer spooler: lpd.
6826 <p>When something is executed</p>
6829 There are several examples where you have to run a
6830 program at system startup or shutdown to perform a
6831 specific task, for example, setting the system's clock
6832 using <prgn>netdate</prgn> or killing all processes
6833 when the system shuts down. Your message should look
6835 <example compact="compact">
6836 Doing something very useful...done.
6838 You should print the <tt>done.</tt> immediately after
6839 the job has been completed, so that the user is
6840 informed why they have to wait. You can get this
6842 <example compact="compact">
6843 echo -n "Doing something very useful..."
6852 <p>When the configuration is reloaded</p>
6855 When a daemon is forced to reload its configuration
6856 files you should use the following format:
6857 <example compact="compact">
6858 Reloading <var>description</var> configuration...done.
6860 where <var>description</var> is the same as in the
6861 daemon starting message.
6869 <heading>Cron jobs</heading>
6872 Packages must not modify the configuration file
6873 <file>/etc/crontab</file>, and they must not modify the files in
6874 <file>/var/spool/cron/crontabs</file>.</p>
6877 If a package wants to install a job that has to be executed
6878 via cron, it should place a file with the name of the
6879 package in one or more of the following directories:
6880 <example compact="compact">
6886 As these directory names imply, the files within them are
6887 executed on an hourly, daily, weekly, or monthly basis,
6888 respectively. The exact times are listed in
6889 <file>/etc/crontab</file>.</p>
6892 All files installed in any of these directories must be
6893 scripts (e.g., shell scripts or Perl scripts) so that they
6894 can easily be modified by the local system administrator.
6895 In addition, they must be treated as configuration files.
6899 If a certain job has to be executed at some other frequency or
6900 at a specific time, the package should install a file
6901 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6902 same syntax as <file>/etc/crontab</file> and is processed by
6903 <prgn>cron</prgn> automatically. The file must also be
6904 treated as a configuration file. (Note that entries in the
6905 <file>/etc/cron.d</file> directory are not handled by
6906 <prgn>anacron</prgn>. Thus, you should only use this
6907 directory for jobs which may be skipped if the system is not
6910 Unlike <file>crontab</file> files described in the IEEE Std
6911 1003.1-2008 (POSIX.1) available from
6912 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6913 name="The Open Group">, the files in
6914 <file>/etc/cron.d</file> and the file
6915 <file>/etc/crontab</file> have seven fields; namely:
6917 <item>Minute [0,59]</item>
6918 <item>Hour [0,23]</item>
6919 <item>Day of the month [1,31]</item>
6920 <item>Month of the year [1,12]</item>
6921 <item>Day of the week ([0,6] with 0=Sunday)</item>
6922 <item>Username</item>
6923 <item>Command to be run</item>
6925 Ranges of numbers are allowed. Ranges are two numbers
6926 separated with a hyphen. The specified range is inclusive.
6927 Lists are allowed. A list is a set of numbers (or ranges)
6928 separated by commas. Step values can be used in conjunction
6933 The scripts or <tt>crontab</tt> entries in these directories should
6934 check if all necessary programs are installed before they
6935 try to execute them. Otherwise, problems will arise when a
6936 package was removed but not purged since configuration files
6937 are kept on the system in this situation.
6941 Any <tt>cron</tt> daemon must provide
6942 <file>/usr/bin/crontab</file> and support normal
6943 <tt>crontab</tt> entries as specified in POSIX. The daemon
6944 must also support names for days and months, ranges, and
6945 step values. It has to support <file>/etc/crontab</file>,
6946 and correctly execute the scripts in
6947 <file>/etc/cron.d</file>. The daemon must also correctly
6949 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6954 <heading>Menus</heading>
6957 The Debian <tt>menu</tt> package provides a standard
6958 interface between packages providing applications and
6959 <em>menu programs</em> (either X window managers or
6960 text-based menu programs such as <prgn>pdmenu</prgn>).
6964 All packages that provide applications that need not be
6965 passed any special command line arguments for normal
6966 operation should register a menu entry for those
6967 applications, so that users of the <tt>menu</tt> package
6968 will automatically get menu entries in their window
6969 managers, as well in shells like <tt>pdmenu</tt>.
6973 Menu entries should follow the current menu policy.
6977 The menu policy can be found in the <tt>menu-policy</tt>
6978 files in the <tt>debian-policy</tt> package.
6979 It is also available from the Debian web mirrors at
6980 <tt><url name="/doc/packaging-manuals/menu-policy/"
6981 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6985 Please also refer to the <em>Debian Menu System</em>
6986 documentation that comes with the <package>menu</package>
6987 package for information about how to register your
6993 <heading>Multimedia handlers</heading>
6996 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6997 is a mechanism for encoding files and data streams and
6998 providing meta-information about them, in particular their
6999 type (e.g. audio or video) and format (e.g. PNG, HTML,
7004 Registration of MIME type handlers allows programs like mail
7005 user agents and web browsers to invoke these handlers to
7006 view, edit or display MIME types they don't support directly.
7010 Packages which provide the ability to view/show/play,
7011 compose, edit or print MIME types should register themselves
7012 as such following the current MIME support policy.
7016 The MIME support policy can be found in the <tt>mime-policy</tt>
7017 files in the <tt>debian-policy</tt> package.
7018 It is also available from the Debian web mirrors at
7019 <tt><url name="/doc/packaging-manuals/mime-policy/"
7020 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7026 <heading>Keyboard configuration</heading>
7029 To achieve a consistent keyboard configuration so that all
7030 applications interpret a keyboard event the same way, all
7031 programs in the Debian distribution must be configured to
7032 comply with the following guidelines.
7036 The following keys must have the specified interpretations:
7039 <tag><tt><--</tt></tag>
7040 <item>delete the character to the left of the cursor</item>
7042 <tag><tt>Delete</tt></tag>
7043 <item>delete the character to the right of the cursor</item>
7045 <tag><tt>Control+H</tt></tag>
7046 <item>emacs: the help prefix</item>
7049 The interpretation of any keyboard events should be
7050 independent of the terminal that is used, be it a virtual
7051 console, an X terminal emulator, an rlogin/telnet session,
7056 The following list explains how the different programs
7057 should be set up to achieve this:
7063 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7067 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7071 X translations are set up to make
7072 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7073 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7074 is the vt220 escape code for the "delete character"
7075 key). This must be done by loading the X resources
7076 using <prgn>xrdb</prgn> on all local X displays, not
7077 using the application defaults, so that the
7078 translation resources used correspond to the
7079 <prgn>xmodmap</prgn> settings.
7083 The Linux console is configured to make
7084 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7085 generate <tt>ESC [ 3 ~</tt>.
7089 X applications are configured so that <tt><</tt>
7090 deletes left, and <tt>Delete</tt> deletes right. Motif
7091 applications already work like this.
7095 Terminals should have <tt>stty erase ^?</tt> .
7099 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7100 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7101 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7105 Emacs is programmed to map <tt>KB_Backspace</tt> or
7106 the <tt>stty erase</tt> character to
7107 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7108 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7109 <tt>^H</tt> to <tt>help</tt> as always.
7113 Other applications use the <tt>stty erase</tt>
7114 character and <tt>kdch1</tt> for the two delete keys,
7115 with ASCII DEL being "delete previous character" and
7116 <tt>kdch1</tt> being "delete character under
7124 This will solve the problem except for the following
7131 Some terminals have a <tt><--</tt> key that cannot
7132 be made to produce anything except <tt>^H</tt>. On
7133 these terminals Emacs help will be unavailable on
7134 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7135 character takes precedence in Emacs, and has been set
7136 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7137 available) can be used instead.
7141 Some operating systems use <tt>^H</tt> for <tt>stty
7142 erase</tt>. However, modern telnet versions and all
7143 rlogin versions propagate <tt>stty</tt> settings, and
7144 almost all UNIX versions honour <tt>stty erase</tt>.
7145 Where the <tt>stty</tt> settings are not propagated
7146 correctly, things can be made to work by using
7147 <tt>stty</tt> manually.
7151 Some systems (including previous Debian versions) use
7152 <prgn>xmodmap</prgn> to arrange for both
7153 <tt><--</tt> and <tt>Delete</tt> to generate
7154 <tt>KB_Delete</tt>. We can change the behavior of
7155 their X clients using the same X resources that we use
7156 to do it for our own clients, or configure our clients
7157 using their resources when things are the other way
7158 around. On displays configured like this
7159 <tt>Delete</tt> will not work, but <tt><--</tt>
7164 Some operating systems have different <tt>kdch1</tt>
7165 settings in their <tt>terminfo</tt> database for
7166 <tt>xterm</tt> and others. On these systems the
7167 <tt>Delete</tt> key will not work correctly when you
7168 log in from a system conforming to our policy, but
7169 <tt><--</tt> will.
7176 <heading>Environment variables</heading>
7179 A program must not depend on environment variables to get
7180 reasonable defaults. (That's because these environment
7181 variables would have to be set in a system-wide
7182 configuration file like <file>/etc/profile</file>, which is not
7183 supported by all shells.)
7187 If a program usually depends on environment variables for its
7188 configuration, the program should be changed to fall back to
7189 a reasonable default configuration if these environment
7190 variables are not present. If this cannot be done easily
7191 (e.g., if the source code of a non-free program is not
7192 available), the program must be replaced by a small
7193 "wrapper" shell script which sets the environment variables
7194 if they are not already defined, and calls the original program.
7198 Here is an example of a wrapper script for this purpose:
7200 <example compact="compact">
7202 BAR=${BAR:-/var/lib/fubar}
7204 exec /usr/lib/foo/foo "$@"
7209 Furthermore, as <file>/etc/profile</file> is a configuration
7210 file of the <prgn>base-files</prgn> package, other packages must
7211 not put any environment variables or other commands into that
7216 <sect id="doc-base">
7217 <heading>Registering Documents using doc-base</heading>
7220 The <package>doc-base</package> package implements a
7221 flexible mechanism for handling and presenting
7222 documentation. The recommended practice is for every Debian
7223 package that provides online documentation (other than just
7224 manual pages) to register these documents with
7225 <package>doc-base</package> by installing a
7226 <package>doc-base</package> control file via the
7227 <prgn/install-docs/ script at installation time and
7228 de-register the manuals again when the package is removed.
7231 Please refer to the documentation that comes with the
7232 <package>doc-base</package> package for information and
7241 <heading>Files</heading>
7243 <sect id="binaries">
7244 <heading>Binaries</heading>
7247 Two different packages must not install programs with
7248 different functionality but with the same filenames. (The
7249 case of two programs having the same functionality but
7250 different implementations is handled via "alternatives" or
7251 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7252 <ref id="conflicts"> respectively.) If this case happens,
7253 one of the programs must be renamed. The maintainers should
7254 report this to the <tt>debian-devel</tt> mailing list and
7255 try to find a consensus about which program will have to be
7256 renamed. If a consensus cannot be reached, <em>both</em>
7257 programs must be renamed.
7261 By default, when a package is being built, any binaries
7262 created should include debugging information, as well as
7263 being compiled with optimization. You should also turn on
7264 as many reasonable compilation warnings as possible; this
7265 makes life easier for porters, who can then look at build
7266 logs for possible problems. For the C programming language,
7267 this means the following compilation parameters should be
7269 <example compact="compact">
7271 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7273 INSTALL = install -s # (or use strip on the files in debian/tmp)
7278 Note that by default all installed binaries should be stripped,
7279 either by using the <tt>-s</tt> flag to
7280 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7281 the binaries after they have been copied into
7282 <file>debian/tmp</file> but before the tree is made into a
7287 Although binaries in the build tree should be compiled with
7288 debugging information by default, it can often be difficult to
7289 debug programs if they are also subjected to compiler
7290 optimization. For this reason, it is recommended to support the
7291 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7292 (see <ref id="debianrules-options">). This variable can contain
7293 several flags to change how a package is compiled and built.
7297 It is up to the package maintainer to decide what
7298 compilation options are best for the package. Certain
7299 binaries (such as computationally-intensive programs) will
7300 function better with certain flags (<tt>-O3</tt>, for
7301 example); feel free to use them. Please use good judgment
7302 here. Don't use flags for the sake of it; only use them
7303 if there is good reason to do so. Feel free to override
7304 the upstream author's ideas about which compilation
7305 options are best: they are often inappropriate for our
7311 <sect id="libraries">
7312 <heading>Libraries</heading>
7315 If the package is <strong>architecture: any</strong>, then
7316 the shared library compilation and linking flags must have
7317 <tt>-fPIC</tt>, or the package shall not build on some of
7318 the supported architectures<footnote>
7320 If you are using GCC, <tt>-fPIC</tt> produces code with
7321 relocatable position independent code, which is required for
7322 most architectures to create a shared library, with i386 and
7323 perhaps some others where non position independent code is
7324 permitted in a shared library.
7327 Position independent code may have a performance penalty,
7328 especially on <tt>i386</tt>. However, in most cases the
7329 speed penalty must be measured against the memory wasted on
7330 the few architectures where non position independent code is
7333 </footnote>. Any exception to this rule must be discussed on
7334 the mailing list <em>debian-devel@lists.debian.org</em>, and
7335 a rough consensus obtained. The reasons for not compiling
7336 with <tt>-fPIC</tt> flag must be recorded in the file
7337 <tt>README.Debian</tt>, and care must be taken to either
7338 restrict the architecture or arrange for <tt>-fPIC</tt> to
7339 be used on architectures where it is required.<footnote>
7341 Some of the reasons why this might be required is if the
7342 library contains hand crafted assembly code that is not
7343 relocatable, the speed penalty is excessive for compute
7344 intensive libs, and similar reasons.
7349 As to the static libraries, the common case is not to have
7350 relocatable code, since there is no benefit, unless in specific
7351 cases; therefore the static version must not be compiled
7352 with the <tt>-fPIC</tt> flag. Any exception to this rule
7353 should be discussed on the mailing list
7354 <em>debian-devel@lists.debian.org</em>, and the reasons for
7355 compiling with the <tt>-fPIC</tt> flag must be recorded in
7356 the file <tt>README.Debian</tt>. <footnote>
7358 Some of the reasons for linking static libraries with
7359 the <tt>-fPIC</tt> flag are if, for example, one needs a
7360 Perl API for a library that is under rapid development,
7361 and has an unstable API, so shared libraries are
7362 pointless at this phase of the library's development. In
7363 that case, since Perl needs a library with relocatable
7364 code, it may make sense to create a static library with
7365 relocatable code. Another reason cited is if you are
7366 distilling various libraries into a common shared
7367 library, like <tt>mklibs</tt> does in the Debian
7373 In other words, if both a shared and a static library is
7374 being built, each source unit (<tt>*.c</tt>, for example,
7375 for C files) will need to be compiled twice, for the normal
7380 Libraries should be built with threading support and to be
7381 thread-safe if the library supports this.
7385 Although not enforced by the build tools, shared libraries
7386 must be linked against all libraries that they use symbols from
7387 in the same way that binaries are. This ensures the correct
7388 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7389 system and guarantees that all libraries can be safely opened
7390 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7391 option <tt>-Wl,-z,defs</tt> when building a shared library.
7392 Since this option enforces symbol resolution at build time,
7393 a missing library reference will be caught early as a fatal
7398 All installed shared libraries should be stripped with
7399 <example compact="compact">
7400 strip --strip-unneeded <var>your-lib</var>
7402 (The option <tt>--strip-unneeded</tt> makes
7403 <prgn>strip</prgn> remove only the symbols which aren't
7404 needed for relocation processing.) Shared libraries can
7405 function perfectly well when stripped, since the symbols for
7406 dynamic linking are in a separate part of the ELF object
7408 You might also want to use the options
7409 <tt>--remove-section=.comment</tt> and
7410 <tt>--remove-section=.note</tt> on both shared libraries
7411 and executables, and <tt>--strip-debug</tt> on static
7417 Note that under some circumstances it may be useful to
7418 install a shared library unstripped, for example when
7419 building a separate package to support debugging.
7423 Shared object files (often <file>.so</file> files) that are not
7424 public libraries, that is, they are not meant to be linked
7425 to by third party executables (binaries of other packages),
7426 should be installed in subdirectories of the
7427 <file>/usr/lib</file> directory. Such files are exempt from the
7428 rules that govern ordinary shared libraries, except that
7429 they must not be installed executable and should be
7431 A common example are the so-called "plug-ins",
7432 internal shared objects that are dynamically loaded by
7433 programs using <manref name="dlopen" section="3">.
7438 Packages that use <prgn>libtool</prgn> to create and install
7439 their shared libraries install a file containing additional
7440 metadata (ending in <file>.la</file>) alongside the library.
7441 For public libraries intended for use by other packages, these
7442 files normally should not be included in the Debian package,
7443 since the information they include is not necessary to link with
7444 the shared library on Debian and can add unnecessary additional
7445 dependencies to other programs or libraries.<footnote>
7446 These files store, among other things, all libraries on which
7447 that shared library depends. Unfortunately, if
7448 the <file>.la</file> file is present and contains that
7449 dependency information, using <prgn>libtool</prgn> when
7450 linking against that library will cause the resulting program
7451 or library to be linked against those dependencies as well,
7452 even if this is unnecessary. This can create unneeded
7453 dependencies on shared library packages that would otherwise
7454 be hidden behind the library ABI, and can make library
7455 transitions to new SONAMEs unnecessarily complicated and
7456 difficult to manage.
7458 If the <file>.la</file> file is required for that library (if,
7459 for instance, it's loaded via <tt>libltdl</tt> in a way that
7460 requires that meta-information), the <tt>dependency_libs</tt>
7461 setting in the <file>.la</file> file should normally be set to
7462 the empty string. If the shared library development package has
7463 historically included the <file>.la</file>, it must be retained
7464 in the development package (with <tt>dependency_libs</tt>
7465 emptied) until all libraries that depend on it have removed or
7466 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7467 files to prevent linking with those other libraries
7468 using <prgn>libtool</prgn> from failing.
7472 If the <file>.la</file> must be included, it should be included
7473 in the development (<tt>-dev</tt>) package, unless the library
7474 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7475 library. If it is intended for use with <tt>libltdl</tt>,
7476 the <file>.la</file> files must go in the run-time library
7481 These requirements for handling of <file>.la</file> files do not
7482 apply to loadable modules or libraries not installed in
7483 directories searched by default by the dynamic linker. Packages
7484 installing loadable modules will frequently need to install
7485 the <file>.la</file> files alongside the modules so that they
7486 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7487 does not need to be modified for libraries or modules that are
7488 not installed in directories searched by the dynamic linker by
7489 default and not intended for use by other packages.
7493 You must make sure that you use only released versions of
7494 shared libraries to build your packages; otherwise other
7495 users will not be able to run your binaries
7496 properly. Producing source packages that depend on
7497 unreleased compilers is also usually a bad
7504 <heading>Shared libraries</heading>
7506 This section has moved to <ref id="sharedlibs">.
7512 <heading>Scripts</heading>
7515 All command scripts, including the package maintainer
7516 scripts inside the package and used by <prgn>dpkg</prgn>,
7517 should have a <tt>#!</tt> line naming the shell to be used
7522 In the case of Perl scripts this should be
7523 <tt>#!/usr/bin/perl</tt>.
7527 When scripts are installed into a directory in the system
7528 PATH, the script name should not include an extension such
7529 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7530 language currently used to implement it.
7533 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7534 <file>init.d</file> scripts should almost certainly start
7535 with <tt>set -e</tt> so that errors are detected.
7536 <file>init.d</file> scripts are something of a special case, due
7537 to how frequently they need to call commands that are allowed to
7538 fail, and it may instead be easier to check the exit status of
7539 commands directly. See <ref id="writing-init"> for more
7540 information about writing <file>init.d</file> scripts.
7543 Every script should use <tt>set -e</tt> or check the exit status
7544 of <em>every</em> command.
7547 Scripts may assume that <file>/bin/sh</file> implements the
7548 SUSv3 Shell Command Language<footnote>
7549 Single UNIX Specification, version 3, which is also IEEE
7550 1003.1-2004 (POSIX), and is available on the World Wide Web
7551 from <url id="http://www.unix.org/version3/online.html"
7552 name="The Open Group"> after free
7553 registration.</footnote>
7554 plus the following additional features not mandated by
7556 These features are in widespread use in the Linux community
7557 and are implemented in all of bash, dash, and ksh, the most
7558 common shells users may wish to use as <file>/bin/sh</file>.
7561 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7562 must not generate a newline.</item>
7563 <item><tt>test</tt>, if implemented as a shell built-in, must
7564 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7566 <item><tt>local</tt> to create a scoped variable must be
7567 supported, including listing multiple variables in a single
7568 local command and assigning a value to a variable at the
7569 same time as localizing it. <tt>local</tt> may or
7570 may not preserve the variable value from an outer scope if
7571 no assignment is present. Uses such as:
7575 # ... use a, b, c, d ...
7578 must be supported and must set the value of <tt>c</tt> to
7581 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7582 -<var>signal</var></tt>, where <var>signal</var> is either
7583 the name of a signal or one of the numeric signals listed in
7584 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7585 supported if <prgn>kill</prgn> is implemented as a shell
7588 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7589 signals must be supported. In addition to the signal
7590 numbers listed in the extension, which are the same as for
7591 <prgn>kill<prgn> above, 13 (SIGPIPE) must be allowed.
7594 If a shell script requires non-SUSv3 features from the shell
7595 interpreter other than those listed above, the appropriate shell
7596 must be specified in the first line of the script (e.g.,
7597 <tt>#!/bin/bash</tt>) and the package must depend on the package
7598 providing the shell (unless the shell package is marked
7599 "Essential", as in the case of <prgn>bash</prgn>).
7603 You may wish to restrict your script to SUSv3 features plus the
7604 above set when possible so that it may use <file>/bin/sh</file>
7605 as its interpreter. If your script works with <prgn>dash</prgn>
7606 (originally called <prgn>ash</prgn>), it probably complies with
7607 the above requirements, but if you are in doubt, use
7608 <file>/bin/bash</file>.
7612 Perl scripts should check for errors when making any
7613 system calls, including <tt>open</tt>, <tt>print</tt>,
7614 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7618 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7619 scripting languages. See <em>Csh Programming Considered
7620 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7621 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7622 If an upstream package comes with <prgn>csh</prgn> scripts
7623 then you must make sure that they start with
7624 <tt>#!/bin/csh</tt> and make your package depend on the
7625 <prgn>c-shell</prgn> virtual package.
7629 Any scripts which create files in world-writeable
7630 directories (e.g., in <file>/tmp</file>) must use a
7631 mechanism which will fail atomically if a file with the same
7632 name already exists.
7636 The Debian base system provides the <prgn>tempfile</prgn>
7637 and <prgn>mktemp</prgn> utilities for use by scripts for
7644 <heading>Symbolic links</heading>
7647 In general, symbolic links within a top-level directory
7648 should be relative, and symbolic links pointing from one
7649 top-level directory into another should be absolute. (A
7650 top-level directory is a sub-directory of the root
7651 directory <file>/</file>.)
7655 In addition, symbolic links should be specified as short as
7656 possible, i.e., link targets like <file>foo/../bar</file> are
7661 Note that when creating a relative link using
7662 <prgn>ln</prgn> it is not necessary for the target of the
7663 link to exist relative to the working directory you're
7664 running <prgn>ln</prgn> from, nor is it necessary to change
7665 directory to the directory where the link is to be made.
7666 Simply include the string that should appear as the target
7667 of the link (this will be a pathname relative to the
7668 directory in which the link resides) as the first argument
7673 For example, in your <prgn>Makefile</prgn> or
7674 <file>debian/rules</file>, you can do things like:
7675 <example compact="compact">
7676 ln -fs gcc $(prefix)/bin/cc
7677 ln -fs gcc debian/tmp/usr/bin/cc
7678 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7679 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7684 A symbolic link pointing to a compressed file should always
7685 have the same file extension as the referenced file. (For
7686 example, if a file <file>foo.gz</file> is referenced by a
7687 symbolic link, the filename of the link has to end with
7688 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7693 <heading>Device files</heading>
7696 Packages must not include device files or named pipes in the
7701 If a package needs any special device files that are not
7702 included in the base system, it must call
7703 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7704 after notifying the user<footnote>
7705 This notification could be done via a (low-priority)
7706 debconf message, or an echo (printf) statement.
7711 Packages must not remove any device files in the
7712 <prgn>postrm</prgn> or any other script. This is left to the
7713 system administrator.
7717 Debian uses the serial devices
7718 <file>/dev/ttyS*</file>. Programs using the old
7719 <file>/dev/cu*</file> devices should be changed to use
7720 <file>/dev/ttyS*</file>.
7724 Named pipes needed by the package must be created in
7725 the <prgn>postinst</prgn> script<footnote>
7726 It's better to use <prgn>mkfifo</prgn> rather
7727 than <prgn>mknod</prgn> to create named pipes so that
7728 automated checks for packages incorrectly creating device
7729 files with <prgn>mknod</prgn> won't have false positives.
7730 </footnote> and removed in
7731 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7736 <sect id="config-files">
7737 <heading>Configuration files</heading>
7740 <heading>Definitions</heading>
7744 <tag>configuration file</tag>
7746 A file that affects the operation of a program, or
7747 provides site- or host-specific information, or
7748 otherwise customizes the behavior of a program.
7749 Typically, configuration files are intended to be
7750 modified by the system administrator (if needed or
7751 desired) to conform to local policy or to provide
7752 more useful site-specific behavior.
7755 <tag><tt>conffile</tt></tag>
7757 A file listed in a package's <tt>conffiles</tt>
7758 file, and is treated specially by <prgn>dpkg</prgn>
7759 (see <ref id="configdetails">).
7765 The distinction between these two is important; they are
7766 not interchangeable concepts. Almost all
7767 <tt>conffile</tt>s are configuration files, but many
7768 configuration files are not <tt>conffiles</tt>.
7772 As noted elsewhere, <file>/etc/init.d</file> scripts,
7773 <file>/etc/default</file> files, scripts installed in
7774 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7775 configuration installed in <file>/etc/cron.d</file> must be
7776 treated as configuration files. In general, any script that
7777 embeds configuration information is de-facto a configuration
7778 file and should be treated as such.
7783 <heading>Location</heading>
7786 Any configuration files created or used by your package
7787 must reside in <file>/etc</file>. If there are several,
7788 consider creating a subdirectory of <file>/etc</file>
7789 named after your package.
7793 If your package creates or uses configuration files
7794 outside of <file>/etc</file>, and it is not feasible to modify
7795 the package to use <file>/etc</file> directly, put the files
7796 in <file>/etc</file> and create symbolic links to those files
7797 from the location that the package requires.
7802 <heading>Behavior</heading>
7805 Configuration file handling must conform to the following
7807 <list compact="compact">
7809 local changes must be preserved during a package
7813 configuration files must be preserved when the
7814 package is removed, and only deleted when the
7818 Obsolete configuration files without local changes may be
7819 removed by the package during upgrade.
7823 The easy way to achieve this behavior is to make the
7824 configuration file a <tt>conffile</tt>. This is
7825 appropriate only if it is possible to distribute a default
7826 version that will work for most installations, although
7827 some system administrators may choose to modify it. This
7828 implies that the default version will be part of the
7829 package distribution, and must not be modified by the
7830 maintainer scripts during installation (or at any other
7835 In order to ensure that local changes are preserved
7836 correctly, no package may contain or make hard links to
7837 conffiles.<footnote>
7838 Rationale: There are two problems with hard links.
7839 The first is that some editors break the link while
7840 editing one of the files, so that the two files may
7841 unwittingly become unlinked and different. The second
7842 is that <prgn>dpkg</prgn> might break the hard link
7843 while upgrading <tt>conffile</tt>s.
7848 The other way to do it is via the maintainer scripts. In
7849 this case, the configuration file must not be listed as a
7850 <tt>conffile</tt> and must not be part of the package
7851 distribution. If the existence of a file is required for
7852 the package to be sensibly configured it is the
7853 responsibility of the package maintainer to provide
7854 maintainer scripts which correctly create, update and
7855 maintain the file and remove it on purge. (See <ref
7856 id="maintainerscripts"> for more information.) These
7857 scripts must be idempotent (i.e., must work correctly if
7858 <prgn>dpkg</prgn> needs to re-run them due to errors
7859 during installation or removal), must cope with all the
7860 variety of ways <prgn>dpkg</prgn> can call maintainer
7861 scripts, must not overwrite or otherwise mangle the user's
7862 configuration without asking, must not ask unnecessary
7863 questions (particularly during upgrades), and must
7864 otherwise be good citizens.
7868 The scripts are not required to configure every possible
7869 option for the package, but only those necessary to get
7870 the package running on a given system. Ideally the
7871 sysadmin should not have to do any configuration other
7872 than that done (semi-)automatically by the
7873 <prgn>postinst</prgn> script.
7877 A common practice is to create a script called
7878 <file><var>package</var>-configure</file> and have the
7879 package's <prgn>postinst</prgn> call it if and only if the
7880 configuration file does not already exist. In certain
7881 cases it is useful for there to be an example or template
7882 file which the maintainer scripts use. Such files should
7883 be in <file>/usr/share/<var>package</var></file> or
7884 <file>/usr/lib/<var>package</var></file> (depending on whether
7885 they are architecture-independent or not). There should
7886 be symbolic links to them from
7887 <file>/usr/share/doc/<var>package</var>/examples</file> if
7888 they are examples, and should be perfectly ordinary
7889 <prgn>dpkg</prgn>-handled files (<em>not</em>
7890 configuration files).
7894 These two styles of configuration file handling must
7895 not be mixed, for that way lies madness:
7896 <prgn>dpkg</prgn> will ask about overwriting the file
7897 every time the package is upgraded.
7902 <heading>Sharing configuration files</heading>
7905 Packages which specify the same file as a
7906 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7907 with each other. (This is an instance of the general rule
7908 about not sharing files. Note that neither alternatives
7909 nor diversions are likely to be appropriate in this case;
7910 in particular, <prgn>dpkg</prgn> does not handle diverted
7911 <tt>conffile</tt>s well.)
7915 The maintainer scripts must not alter a <tt>conffile</tt>
7916 of <em>any</em> package, including the one the scripts
7921 If two or more packages use the same configuration file
7922 and it is reasonable for both to be installed at the same
7923 time, one of these packages must be defined as
7924 <em>owner</em> of the configuration file, i.e., it will be
7925 the package which handles that file as a configuration
7926 file. Other packages that use the configuration file must
7927 depend on the owning package if they require the
7928 configuration file to operate. If the other package will
7929 use the configuration file if present, but is capable of
7930 operating without it, no dependency need be declared.
7934 If it is desirable for two or more related packages to
7935 share a configuration file <em>and</em> for all of the
7936 related packages to be able to modify that configuration
7937 file, then the following should be done:
7938 <enumlist compact="compact">
7940 One of the related packages (the "owning" package)
7941 will manage the configuration file with maintainer
7942 scripts as described in the previous section.
7945 The owning package should also provide a program
7946 that the other packages may use to modify the
7950 The related packages must use the provided program
7951 to make any desired modifications to the
7952 configuration file. They should either depend on
7953 the core package to guarantee that the configuration
7954 modifier program is available or accept gracefully
7955 that they cannot modify the configuration file if it
7956 is not. (This is in addition to the fact that the
7957 configuration file may not even be present in the
7964 Sometimes it's appropriate to create a new package which
7965 provides the basic infrastructure for the other packages
7966 and which manages the shared configuration files. (The
7967 <tt>sgml-base</tt> package is a good example.)
7972 <heading>User configuration files ("dotfiles")</heading>
7975 The files in <file>/etc/skel</file> will automatically be
7976 copied into new user accounts by <prgn>adduser</prgn>.
7977 No other program should reference the files in
7978 <file>/etc/skel</file>.
7982 Therefore, if a program needs a dotfile to exist in
7983 advance in <file>$HOME</file> to work sensibly, that dotfile
7984 should be installed in <file>/etc/skel</file> and treated as a
7989 However, programs that require dotfiles in order to
7990 operate sensibly are a bad thing, unless they do create
7991 the dotfiles themselves automatically.
7995 Furthermore, programs should be configured by the Debian
7996 default installation to behave as closely to the upstream
7997 default behavior as possible.
8001 Therefore, if a program in a Debian package needs to be
8002 configured in some way in order to operate sensibly, that
8003 should be done using a site-wide configuration file placed
8004 in <file>/etc</file>. Only if the program doesn't support a
8005 site-wide default configuration and the package maintainer
8006 doesn't have time to add it may a default per-user file be
8007 placed in <file>/etc/skel</file>.
8011 <file>/etc/skel</file> should be as empty as we can make it.
8012 This is particularly true because there is no easy (or
8013 necessarily desirable) mechanism for ensuring that the
8014 appropriate dotfiles are copied into the accounts of
8015 existing users when a package is installed.
8021 <heading>Log files</heading>
8023 Log files should usually be named
8024 <file>/var/log/<var>package</var>.log</file>. If you have many
8025 log files, or need a separate directory for permission
8026 reasons (<file>/var/log</file> is writable only by
8027 <file>root</file>), you should usually create a directory named
8028 <file>/var/log/<var>package</var></file> and place your log
8033 Log files must be rotated occasionally so that they don't grow
8034 indefinitely. The best way to do this is to install a log
8035 rotation configuration file in the
8036 directory <file>/etc/logrotate.d</file>, normally
8037 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8038 the facilities provided by <prgn>logrotate</prgn>.
8041 The traditional approach to log files has been to set up
8042 <em>ad hoc</em> log rotation schemes using simple shell
8043 scripts and cron. While this approach is highly
8044 customizable, it requires quite a lot of sysadmin work.
8045 Even though the original Debian system helped a little
8046 by automatically installing a system which can be used
8047 as a template, this was deemed not enough.
8051 The use of <prgn>logrotate</prgn>, a program developed
8052 by Red Hat, is better, as it centralizes log management.
8053 It has both a configuration file
8054 (<file>/etc/logrotate.conf</file>) and a directory where
8055 packages can drop their individual log rotation
8056 configurations (<file>/etc/logrotate.d</file>).
8059 Here is a good example for a logrotate config
8060 file (for more information see <manref name="logrotate"
8062 <example compact="compact">
8063 /var/log/foo/*.log {
8069 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8073 This rotates all files under <file>/var/log/foo</file>, saves 12
8074 compressed generations, and tells the daemon to reopen its log
8075 files after the log rotation. It skips this log rotation
8076 (via <tt>missingok</tt>) if no such log file is present, which
8077 avoids errors if the package is removed but not purged.
8081 Log files should be removed when the package is
8082 purged (but not when it is only removed). This should be
8083 done by the <prgn>postrm</prgn> script when it is called
8084 with the argument <tt>purge</tt> (see <ref
8085 id="removedetails">).
8089 <sect id="permissions-owners">
8090 <heading>Permissions and owners</heading>
8093 The rules in this section are guidelines for general use.
8094 If necessary you may deviate from the details below.
8095 However, if you do so you must make sure that what is done
8096 is secure and you should try to be as consistent as possible
8097 with the rest of the system. You should probably also
8098 discuss it on <prgn>debian-devel</prgn> first.
8102 Files should be owned by <tt>root:root</tt>, and made
8103 writable only by the owner and universally readable (and
8104 executable, if appropriate), that is mode 644 or 755.
8108 Directories should be mode 755 or (for group-writability)
8109 mode 2775. The ownership of the directory should be
8110 consistent with its mode: if a directory is mode 2775, it
8111 should be owned by the group that needs write access to
8114 When a package is upgraded, and the owner or permissions
8115 of a file included in the package has changed, dpkg
8116 arranges for the ownership and permissions to be
8117 correctly set upon installation. However, this does not
8118 extend to directories; the permissions and ownership of
8119 directories already on the system does not change on
8120 install or upgrade of packages. This makes sense, since
8121 otherwise common directories like <tt>/usr</tt> would
8122 always be in flux. To correctly change permissions of a
8123 directory the package owns, explicit action is required,
8124 usually in the <tt>postinst</tt> script. Care must be
8125 taken to handle downgrades as well, in that case.
8131 Control information files should be owned by <tt>root:root</tt>
8132 and either mode 644 (for most files) or mode 755 (for
8133 executables such as <qref id="maintscripts">maintainer
8138 Setuid and setgid executables should be mode 4755 or 2755
8139 respectively, and owned by the appropriate user or group.
8140 They should not be made unreadable (modes like 4711 or
8141 2711 or even 4111); doing so achieves no extra security,
8142 because anyone can find the binary in the freely available
8143 Debian package; it is merely inconvenient. For the same
8144 reason you should not restrict read or execute permissions
8145 on non-set-id executables.
8149 Some setuid programs need to be restricted to particular
8150 sets of users, using file permissions. In this case they
8151 should be owned by the uid to which they are set-id, and by
8152 the group which should be allowed to execute them. They
8153 should have mode 4754; again there is no point in making
8154 them unreadable to those users who must not be allowed to
8159 It is possible to arrange that the system administrator can
8160 reconfigure the package to correspond to their local
8161 security policy by changing the permissions on a binary:
8162 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8163 described below.<footnote>
8164 Ordinary files installed by <prgn>dpkg</prgn> (as
8165 opposed to <tt>conffile</tt>s and other similar objects)
8166 normally have their permissions reset to the distributed
8167 permissions when the package is reinstalled. However,
8168 the use of <prgn>dpkg-statoverride</prgn> overrides this
8171 Another method you should consider is to create a group for
8172 people allowed to use the program(s) and make any setuid
8173 executables executable only by that group.
8177 If you need to create a new user or group for your package
8178 there are two possibilities. Firstly, you may need to
8179 make some files in the binary package be owned by this
8180 user or group, or you may need to compile the user or
8181 group id (rather than just the name) into the binary
8182 (though this latter should be avoided if possible, as in
8183 this case you need a statically allocated id).</p>
8186 If you need a statically allocated id, you must ask for a
8187 user or group id from the <tt>base-passwd</tt> maintainer,
8188 and must not release the package until you have been
8189 allocated one. Once you have been allocated one you must
8190 either make the package depend on a version of the
8191 <tt>base-passwd</tt> package with the id present in
8192 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8193 your package to create the user or group itself with the
8194 correct id (using <tt>adduser</tt>) in its
8195 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8196 the <prgn>postinst</prgn> is to be preferred if it is
8197 possible, otherwise a pre-dependency will be needed on the
8198 <tt>adduser</tt> package.)
8202 On the other hand, the program might be able to determine
8203 the uid or gid from the user or group name at runtime, so
8204 that a dynamically allocated id can be used. In this case
8205 you should choose an appropriate user or group name,
8206 discussing this on <prgn>debian-devel</prgn> and checking
8207 with the <package/base-passwd/ maintainer that it is unique and that
8208 they do not wish you to use a statically allocated id
8209 instead. When this has been checked you must arrange for
8210 your package to create the user or group if necessary using
8211 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8212 <prgn>postinst</prgn> script (again, the latter is to be
8213 preferred if it is possible).
8217 Note that changing the numeric value of an id associated
8218 with a name is very difficult, and involves searching the
8219 file system for all appropriate files. You need to think
8220 carefully whether a static or dynamic id is required, since
8221 changing your mind later will cause problems.
8224 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8226 This section is not intended as policy, but as a
8227 description of the use of <prgn>dpkg-statoverride</prgn>.
8231 If a system administrator wishes to have a file (or
8232 directory or other such thing) installed with owner and
8233 permissions different from those in the distributed Debian
8234 package, they can use the <prgn>dpkg-statoverride</prgn>
8235 program to instruct <prgn>dpkg</prgn> to use the different
8236 settings every time the file is installed. Thus the
8237 package maintainer should distribute the files with their
8238 normal permissions, and leave it for the system
8239 administrator to make any desired changes. For example, a
8240 daemon which is normally required to be setuid root, but
8241 in certain situations could be used without being setuid,
8242 should be installed setuid in the <tt>.deb</tt>. Then the
8243 local system administrator can change this if they wish.
8244 If there are two standard ways of doing it, the package
8245 maintainer can use <tt>debconf</tt> to find out the
8246 preference, and call <prgn>dpkg-statoverride</prgn> in the
8247 maintainer script if necessary to accommodate the system
8248 administrator's choice. Care must be taken during
8249 upgrades to not override an existing setting.
8253 Given the above, <prgn>dpkg-statoverride</prgn> is
8254 essentially a tool for system administrators and would not
8255 normally be needed in the maintainer scripts. There is
8256 one type of situation, though, where calls to
8257 <prgn>dpkg-statoverride</prgn> would be needed in the
8258 maintainer scripts, and that involves packages which use
8259 dynamically allocated user or group ids. In such a
8260 situation, something like the following idiom can be very
8261 helpful in the package's <prgn>postinst</prgn>, where
8262 <tt>sysuser</tt> is a dynamically allocated id:
8264 for i in /usr/bin/foo /usr/sbin/bar
8266 # only do something when no setting exists
8267 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8269 #include: debconf processing, question about foo and bar
8270 if [ "$RET" = "true" ] ; then
8271 dpkg-statoverride --update --add sysuser root 4755 $i
8276 The corresponding code to remove the override when the package
8279 for i in /usr/bin/foo /usr/sbin/bar
8281 if dpkg-statoverride --list $i >/dev/null 2>&1
8283 dpkg-statoverride --remove $i
8293 <chapt id="customized-programs">
8294 <heading>Customized programs</heading>
8296 <sect id="arch-spec">
8297 <heading>Architecture specification strings</heading>
8300 If a program needs to specify an <em>architecture specification
8301 string</em> in some place, it should select one of the strings
8302 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8303 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8304 part is sometimes elided, as when the OS is Linux.
8308 Note that we don't want to use
8309 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8310 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8311 since this would make our programs incompatible with other
8312 Linux distributions. We also don't use something like
8313 <tt><var>arch</var>-unknown-linux</tt>, since the
8314 <tt>unknown</tt> does not look very good.
8317 <sect1 id="arch-wildcard-spec">
8318 <heading>Architecture wildcards</heading>
8321 A package may specify an architecture wildcard. Architecture
8322 wildcards are in the format <tt>any</tt> (which matches every
8323 architecture), <tt><var>os</var></tt>-any, or
8324 any-<tt><var>cpu</var></tt>. <footnote>
8325 Internally, the package system normalizes the GNU triplets
8326 and the Debian arches into Debian arch triplets (which are
8327 kind of inverted GNU triplets), with the first component of
8328 the triplet representing the libc and ABI in use, and then
8329 does matching against those triplets. However, such
8330 triplets are an internal implementation detail that should
8331 not be used by packages directly. The libc and ABI portion
8332 is handled internally by the package system based on
8333 the <var>os</var> and <var>cpu</var>.
8340 <heading>Daemons</heading>
8343 The configuration files <file>/etc/services</file>,
8344 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8345 by the <prgn>netbase</prgn> package and must not be modified
8350 If a package requires a new entry in one of these files, the
8351 maintainer should get in contact with the
8352 <prgn>netbase</prgn> maintainer, who will add the entries
8353 and release a new version of the <prgn>netbase</prgn>
8358 The configuration file <file>/etc/inetd.conf</file> must not be
8359 modified by the package's scripts except via the
8360 <prgn>update-inetd</prgn> script or the
8361 <file>DebianNet.pm</file> Perl module. See their documentation
8362 for details on how to add entries.
8366 If a package wants to install an example entry into
8367 <file>/etc/inetd.conf</file>, the entry must be preceded with
8368 exactly one hash character (<tt>#</tt>). Such lines are
8369 treated as "commented out by user" by the
8370 <prgn>update-inetd</prgn> script and are not changed or
8371 activated during package updates.
8376 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8380 Some programs need to create pseudo-ttys. This should be done
8381 using Unix98 ptys if the C library supports it. The resulting
8382 program must not be installed setuid root, unless that
8383 is required for other functionality.
8387 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8388 <file>/var/log/lastlog</file> must be installed writable by
8389 group <tt>utmp</tt>. Programs which need to modify those
8390 files must be installed setgid <tt>utmp</tt>.
8395 <heading>Editors and pagers</heading>
8398 Some programs have the ability to launch an editor or pager
8399 program to edit or display a text document. Since there are
8400 lots of different editors and pagers available in the Debian
8401 distribution, the system administrator and each user should
8402 have the possibility to choose their preferred editor and
8407 In addition, every program should choose a good default
8408 editor/pager if none is selected by the user or system
8413 Thus, every program that launches an editor or pager must
8414 use the EDITOR or PAGER environment variable to determine
8415 the editor or pager the user wishes to use. If these
8416 variables are not set, the programs <file>/usr/bin/editor</file>
8417 and <file>/usr/bin/pager</file> should be used, respectively.
8421 These two files are managed through the <prgn>dpkg</prgn>
8422 "alternatives" mechanism. Every package providing an editor or
8423 pager must call the <prgn>update-alternatives</prgn> script to
8424 register as an alternative for <file>/usr/bin/editor</file>
8425 or <file>/usr/bin/pager</file> as appropriate. The alternative
8426 should have a slave alternative
8427 for <file>/usr/share/man/man1/editor.1.gz</file>
8428 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8429 corresponding manual page.
8433 If it is very hard to adapt a program to make use of the
8434 EDITOR or PAGER variables, that program may be configured to
8435 use <file>/usr/bin/sensible-editor</file> and
8436 <file>/usr/bin/sensible-pager</file> as the editor or pager
8437 program respectively. These are two scripts provided in the
8438 <package>sensible-utils</package> package that check the EDITOR
8439 and PAGER variables and launch the appropriate program, and fall
8440 back to <file>/usr/bin/editor</file>
8441 and <file>/usr/bin/pager</file> if the variable is not set.
8445 A program may also use the VISUAL environment variable to
8446 determine the user's choice of editor. If it exists, it
8447 should take precedence over EDITOR. This is in fact what
8448 <file>/usr/bin/sensible-editor</file> does.
8452 It is not required for a package to depend on
8453 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8454 package to provide such virtual packages.<footnote>
8455 The Debian base system already provides an editor and a
8461 <sect id="web-appl">
8462 <heading>Web servers and applications</heading>
8465 This section describes the locations and URLs that should
8466 be used by all web servers and web applications in the
8473 Cgi-bin executable files are installed in the
8475 <example compact="compact">
8476 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8478 or a subdirectory of that directory, and should be
8480 <example compact="compact">
8481 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8483 (possibly with a subdirectory name
8484 before <var>cgi-bin-name</var>).
8488 <p>Access to HTML documents</p>
8491 HTML documents for a package are stored in
8492 <file>/usr/share/doc/<var>package</var></file>
8493 and can be referred to as
8494 <example compact="compact">
8495 http://localhost/doc/<var>package</var>/<var>filename</var>
8500 The web server should restrict access to the document
8501 tree so that only clients on the same host can read
8502 the documents. If the web server does not support such
8503 access controls, then it should not provide access at
8504 all, or ask about providing access during installation.
8509 <p>Access to images</p>
8511 It is recommended that images for a package be stored
8512 in <tt>/usr/share/images/<var>package</var></tt> and
8513 may be referred to through an alias <tt>/images/</tt>
8516 http://localhost/images/<package>/<filename>
8523 <p>Web Document Root</p>
8526 Web Applications should try to avoid storing files in
8527 the Web Document Root. Instead they should use the
8528 /usr/share/doc/<var>package</var> directory for
8529 documents and register the Web Application via the
8530 <package>doc-base</package> package. If access to the
8531 web document root is unavoidable then use
8532 <example compact="compact">
8535 as the Document Root. This might be just a symbolic
8536 link to the location where the system administrator
8537 has put the real document root.
8540 <item><p>Providing httpd and/or httpd-cgi</p>
8542 All web servers should provide the virtual package
8543 <tt>httpd</tt>. If a web server has CGI support it should
8544 provide <tt>httpd-cgi</tt> additionally.
8547 All web applications which do not contain CGI scripts should
8548 depend on <tt>httpd</tt>, all those web applications which
8549 <tt>do</tt> contain CGI scripts, should depend on
8557 <sect id="mail-transport-agents">
8558 <heading>Mail transport, delivery and user agents</heading>
8561 Debian packages which process electronic mail, whether mail
8562 user agents (MUAs) or mail transport agents (MTAs), must
8563 ensure that they are compatible with the configuration
8564 decisions below. Failure to do this may result in lost
8565 mail, broken <tt>From:</tt> lines, and other serious brain
8570 The mail spool is <file>/var/mail</file> and the interface to
8571 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8572 the FHS). On older systems, the mail spool may be
8573 physically located in <file>/var/spool/mail</file>, but all
8574 access to the mail spool should be via the
8575 <file>/var/mail</file> symlink. The mail spool is part of the
8576 base system and not part of the MTA package.
8580 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8581 programs (such as IMAP daemons) must lock the mailbox in an
8582 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8583 be combined with dot locking. To avoid deadlocks, a program
8584 should use <tt>fcntl()</tt> first and dot locking after
8585 this, or alternatively implement the two locking methods in
8586 a non blocking way<footnote>
8587 If it is not possible to establish both locks, the
8588 system shouldn't wait for the second lock to be
8589 established, but remove the first lock, wait a (random)
8590 time, and start over locking again.
8591 </footnote>. Using the functions <tt>maillock</tt> and
8592 <tt>mailunlock</tt> provided by the
8593 <tt>liblockfile*</tt><footnote>
8594 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8595 to use these functions.
8596 </footnote> packages is the recommended way to realize this.
8600 Mailboxes are generally either mode 600 and owned by
8601 <var>user</var> or mode 660 and owned by
8602 <tt><var>user</var>:mail</tt><footnote>
8603 There are two traditional permission schemes for mail spools:
8604 mode 600 with all mail delivery done by processes running as
8605 the destination user, or mode 660 and owned by group mail with
8606 mail delivery done by a process running as a system user in
8607 group mail. Historically, Debian required mode 660 mail
8608 spools to enable the latter model, but that model has become
8609 increasingly uncommon and the principle of least privilege
8610 indicates that mail systems that use the first model should
8611 use permissions of 600. If delivery to programs is permitted,
8612 it's easier to keep the mail system secure if the delivery
8613 agent runs as the destination user. Debian Policy therefore
8614 permits either scheme.
8615 </footnote>. The local system administrator may choose a
8616 different permission scheme; packages should not make
8617 assumptions about the permission and ownership of mailboxes
8618 unless required (such as when creating a new mailbox). A MUA
8619 may remove a mailbox (unless it has nonstandard permissions) in
8620 which case the MTA or another MUA must recreate it if needed.
8624 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8625 be setgid mail to do the locking mentioned above (and
8626 must obviously avoid accessing other users' mailboxes
8627 using this privilege).</p>
8630 <file>/etc/aliases</file> is the source file for the system mail
8631 aliases (e.g., postmaster, usenet, etc.), it is the one
8632 which the sysadmin and <prgn>postinst</prgn> scripts may
8633 edit. After <file>/etc/aliases</file> is edited the program or
8634 human editing it must call <prgn>newaliases</prgn>. All MTA
8635 packages must come with a <prgn>newaliases</prgn> program,
8636 even if it does nothing, but older MTA packages did not do
8637 this so programs should not fail if <prgn>newaliases</prgn>
8638 cannot be found. Note that because of this, all MTA
8639 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8640 <tt>Replaces: mail-transport-agent</tt> control fields.
8644 The convention of writing <tt>forward to
8645 <var>address</var></tt> in the mailbox itself is not
8646 supported. Use a <tt>.forward</tt> file instead.</p>
8649 The <prgn>rmail</prgn> program used by UUCP
8650 for incoming mail should be <file>/usr/sbin/rmail</file>.
8651 Likewise, <prgn>rsmtp</prgn>, for receiving
8652 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8656 If your package needs to know what hostname to use on (for
8657 example) outgoing news and mail messages which are generated
8658 locally, you should use the file <file>/etc/mailname</file>. It
8659 will contain the portion after the username and <tt>@</tt>
8660 (at) sign for email addresses of users on the machine
8661 (followed by a newline).
8665 Such a package should check for the existence of this file
8666 when it is being configured. If it exists, it should be
8667 used without comment, although an MTA's configuration script
8668 may wish to prompt the user even if it finds that this file
8669 exists. If the file does not exist, the package should
8670 prompt the user for the value (preferably using
8671 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8672 as well as using it in the package's configuration. The
8673 prompt should make it clear that the name will not just be
8674 used by that package. For example, in this situation the
8675 <tt>inn</tt> package could say something like:
8676 <example compact="compact">
8677 Please enter the "mail name" of your system. This is the
8678 hostname portion of the address to be shown on outgoing
8679 news and mail messages. The default is
8680 <var>syshostname</var>, your system's host name. Mail
8681 name ["<var>syshostname</var>"]:
8683 where <var>syshostname</var> is the output of <tt>hostname
8689 <heading>News system configuration</heading>
8692 All the configuration files related to the NNTP (news)
8693 servers and clients should be located under
8694 <file>/etc/news</file>.</p>
8697 There are some configuration issues that apply to a number
8698 of news clients and server packages on the machine. These
8702 <tag><file>/etc/news/organization</file></tag>
8704 A string which should appear as the
8705 organization header for all messages posted
8706 by NNTP clients on the machine
8709 <tag><file>/etc/news/server</file></tag>
8711 Contains the FQDN of the upstream NNTP
8712 server, or localhost if the local machine is
8717 Other global files may be added as required for cross-package news
8724 <heading>Programs for the X Window System</heading>
8727 <heading>Providing X support and package priorities</heading>
8730 Programs that can be configured with support for the X
8731 Window System must be configured to do so and must declare
8732 any package dependencies necessary to satisfy their
8733 runtime requirements when using the X Window System. If
8734 such a package is of higher priority than the X packages
8735 on which it depends, it is required that either the
8736 X-specific components be split into a separate package, or
8737 that an alternative version of the package, which includes
8738 X support, be provided, or that the package's priority be
8744 <heading>Packages providing an X server</heading>
8747 Packages that provide an X server that, directly or
8748 indirectly, communicates with real input and display
8749 hardware should declare in their <tt>Provides</tt> control
8750 field that they provide the virtual
8751 package <tt>xserver</tt>.<footnote>
8752 This implements current practice, and provides an
8753 actual policy for usage of the <tt>xserver</tt>
8754 virtual package which appears in the virtual packages
8755 list. In a nutshell, X servers that interface
8756 directly with the display and input hardware or via
8757 another subsystem (e.g., GGI) should provide
8758 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8759 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8765 <heading>Packages providing a terminal emulator</heading>
8768 Packages that provide a terminal emulator for the X Window
8769 System which meet the criteria listed below should declare in
8770 their <tt>Provides</tt> control field that they provide the
8771 virtual package <tt>x-terminal-emulator</tt>. They should
8772 also register themselves as an alternative for
8773 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8774 20. That alternative should have a slave alternative
8775 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8776 pointing to the corresponding manual page.
8780 To be an <tt>x-terminal-emulator</tt>, a program must:
8781 <list compact="compact">
8783 Be able to emulate a DEC VT100 terminal, or a
8784 compatible terminal.
8788 Support the command-line option <tt>-e
8789 <var>command</var></tt>, which creates a new
8790 terminal window<footnote>
8791 "New terminal window" does not necessarily mean
8792 a new top-level X window directly parented by
8793 the window manager; it could, if the terminal
8794 emulator application were so coded, be a new
8795 "view" in a multiple-document interface (MDI).
8797 and runs the specified <var>command</var>,
8798 interpreting the entirety of the rest of the command
8799 line as a command to pass straight to exec, in the
8800 manner that <tt>xterm</tt> does.
8804 Support the command-line option <tt>-T
8805 <var>title</var></tt>, which creates a new terminal
8806 window with the window title <var>title</var>.
8813 <heading>Packages providing a window manager</heading>
8816 Packages that provide a window manager should declare in
8817 their <tt>Provides</tt> control field that they provide the
8818 virtual package <tt>x-window-manager</tt>. They should also
8819 register themselves as an alternative for
8820 <file>/usr/bin/x-window-manager</file>, with a priority
8821 calculated as follows:
8822 <list compact="compact">
8824 Start with a priority of 20.
8828 If the window manager supports the Debian menu
8829 system, add 20 points if this support is available
8830 in the package's default configuration (i.e., no
8831 configuration files belonging to the system or user
8832 have to be edited to activate the feature); if
8833 configuration files must be modified, add only 10
8839 If the window manager complies with <url
8840 id="http://www.freedesktop.org/Standards/wm-spec"
8841 name="The Window Manager Specification Project">,
8842 written by the <url id="http://www.freedesktop.org/"
8843 name="Free Desktop Group">, add 40 points.
8847 If the window manager permits the X session to be
8848 restarted using a <em>different</em> window manager
8849 (without killing the X server) in its default
8850 configuration, add 10 points; otherwise add none.
8853 That alternative should have a slave alternative
8854 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8855 pointing to the corresponding manual page.
8860 <heading>Packages providing fonts</heading>
8863 Packages that provide fonts for the X Window
8865 For the purposes of Debian Policy, a "font for the X
8866 Window System" is one which is accessed via X protocol
8867 requests. Fonts for the Linux console, for PostScript
8868 renderer, or any other purpose, do not fit this
8869 definition. Any tool which makes such fonts available
8870 to the X Window System, however, must abide by this
8873 must do a number of things to ensure that they are both
8874 available without modification of the X or font server
8875 configuration, and that they do not corrupt files used by
8876 other font packages to register information about
8880 Fonts of any type supported by the X Window System
8881 must be in a separate binary package from any
8882 executables, libraries, or documentation (except
8883 that specific to the fonts shipped, such as their
8884 license information). If one or more of the fonts
8885 so packaged are necessary for proper operation of
8886 the package with which they are associated the font
8887 package may be Recommended; if the fonts merely
8888 provide an enhancement, a Suggests relationship may
8889 be used. Packages must not Depend on font
8891 This is because the X server may retrieve fonts
8892 from the local file system or over the network
8893 from an X font server; the Debian package system
8894 is empowered to deal only with the local
8900 BDF fonts must be converted to PCF fonts with the
8901 <prgn>bdftopcf</prgn> utility (available in the
8902 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8903 placed in a directory that corresponds to their
8905 <list compact="compact">
8907 100 dpi fonts must be placed in
8908 <file>/usr/share/fonts/X11/100dpi/</file>.
8912 75 dpi fonts must be placed in
8913 <file>/usr/share/fonts/X11/75dpi/</file>.
8917 Character-cell fonts, cursor fonts, and other
8918 low-resolution fonts must be placed in
8919 <file>/usr/share/fonts/X11/misc/</file>.
8925 Type 1 fonts must be placed in
8926 <file>/usr/share/fonts/X11/Type1/</file>. If font
8927 metric files are available, they must be placed here
8932 Subdirectories of <file>/usr/share/fonts/X11/</file>
8933 other than those listed above must be neither
8934 created nor used. (The <file>PEX</file>, <file>CID</file>,
8935 <file>Speedo</file>, and <file>cyrillic</file> directories
8936 are excepted for historical reasons, but installation of
8937 files into these directories remains discouraged.)
8941 Font packages may, instead of placing files directly
8942 in the X font directories listed above, provide
8943 symbolic links in that font directory pointing to
8944 the files' actual location in the filesystem. Such
8945 a location must comply with the FHS.
8949 Font packages should not contain both 75dpi and
8950 100dpi versions of a font. If both are available,
8951 they should be provided in separate binary packages
8952 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8953 the names of the packages containing the
8954 corresponding fonts.
8958 Fonts destined for the <file>misc</file> subdirectory
8959 should not be included in the same package as 75dpi
8960 or 100dpi fonts; instead, they should be provided in
8961 a separate package with <tt>-misc</tt> appended to
8966 Font packages must not provide the files
8967 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8968 <file>fonts.scale</file> in a font directory:
8971 <file>fonts.dir</file> files must not be provided at all.
8975 <file>fonts.alias</file> and <file>fonts.scale</file>
8976 files, if needed, should be provided in the
8978 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8979 where <var>fontdir</var> is the name of the
8981 <file>/usr/share/fonts/X11/</file> where the
8982 package's corresponding fonts are stored
8983 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8984 <var>package</var> is the name of the package
8985 that provides these fonts, and
8986 <var>extension</var> is either <tt>scale</tt>
8987 or <tt>alias</tt>, whichever corresponds to
8994 Font packages must declare a dependency on
8995 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
8996 or <tt>Pre-Depends</tt> control field.
9000 Font packages that provide one or more
9001 <file>fonts.scale</file> files as described above must
9002 invoke <prgn>update-fonts-scale</prgn> on each
9003 directory into which they installed fonts
9004 <em>before</em> invoking
9005 <prgn>update-fonts-dir</prgn> on that directory.
9006 This invocation must occur in both the
9007 <prgn>postinst</prgn> (for all arguments) and
9008 <prgn>postrm</prgn> (for all arguments except
9009 <tt>upgrade</tt>) scripts.
9013 Font packages that provide one or more
9014 <file>fonts.alias</file> files as described above must
9015 invoke <prgn>update-fonts-alias</prgn> on each
9016 directory into which they installed fonts. This
9017 invocation must occur in both the
9018 <prgn>postinst</prgn> (for all arguments) and
9019 <prgn>postrm</prgn> (for all arguments except
9020 <tt>upgrade</tt>) scripts.
9024 Font packages must invoke
9025 <prgn>update-fonts-dir</prgn> on each directory into
9026 which they installed fonts. This invocation must
9027 occur in both the <prgn>postinst</prgn> (for all
9028 arguments) and <prgn>postrm</prgn> (for all
9029 arguments except <tt>upgrade</tt>) scripts.
9033 Font packages must not provide alias names for the
9034 fonts they include which collide with alias names
9035 already in use by fonts already packaged.
9039 Font packages must not provide fonts with the same
9040 XLFD registry name as another font already packaged.
9046 <sect1 id="appdefaults">
9047 <heading>Application defaults files</heading>
9050 Application defaults files must be installed in the
9051 directory <file>/etc/X11/app-defaults/</file> (use of a
9052 localized subdirectory of <file>/etc/X11/</file> as described
9053 in the <em>X Toolkit Intrinsics - C Language
9054 Interface</em> manual is also permitted). They must be
9055 registered as <tt>conffile</tt>s or handled as
9056 configuration files.
9060 Customization of programs' X resources may also be
9061 supported with the provision of a file with the same name
9062 as that of the package placed in
9063 the <file>/etc/X11/Xresources/</file> directory, which
9064 must be registered as a <tt>conffile</tt> or handled as a
9065 configuration file.<footnote>
9066 Note that this mechanism is not the same as using
9067 app-defaults; app-defaults are tied to the client
9068 binary on the local file system, whereas X resources
9069 are stored in the X server and affect all connecting
9076 <heading>Installation directory issues</heading>
9079 Historically, packages using the X Window System used a
9080 separate set of installation directories from other packages.
9081 This practice has been discontinued and packages using the X
9082 Window System should now generally be installed in the same
9083 directories as any other package. Specifically, packages must
9084 not install files under the <file>/usr/X11R6/</file> directory
9085 and the <file>/usr/X11R6/</file> directory hierarchy should be
9086 regarded as obsolete.
9090 Include files previously installed under
9091 <file>/usr/X11R6/include/X11/</file> should be installed into
9092 <file>/usr/include/X11/</file>. For files previously
9093 installed into subdirectories of
9094 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9095 determine if subdirectories of <file>/usr/lib/</file> and
9096 <file>/usr/share/</file> can be used. If not, a subdirectory
9097 of <file>/usr/lib/X11/</file> should be used.
9101 Configuration files for window, display, or session managers
9102 or other applications that are tightly integrated with the X
9103 Window System may be placed in a subdirectory
9104 of <file>/etc/X11/</file> corresponding to the package name.
9105 Other X Window System applications should use
9106 the <file>/etc/</file> directory unless otherwise mandated by
9107 policy (such as for <ref id="appdefaults">).
9112 <heading>The OSF/Motif and OpenMotif libraries</heading>
9115 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9116 OpenMotif libraries</em><footnote>
9117 OSF/Motif and OpenMotif are collectively referred to as
9118 "Motif" in this policy document.
9120 should be compiled against and tested with LessTif (a free
9121 re-implementation of Motif) instead. If the maintainer
9122 judges that the program or programs do not work
9123 sufficiently well with LessTif to be distributed and
9124 supported, but do so when compiled against Motif, then two
9125 versions of the package should be created; one linked
9126 statically against Motif and with <tt>-smotif</tt>
9127 appended to the package name, and one linked dynamically
9128 against Motif and with <tt>-dmotif</tt> appended to the
9133 Both Motif-linked versions are dependent
9134 upon non-DFSG-compliant software and thus cannot be
9135 uploaded to the <em>main</em> distribution; if the
9136 software is itself DFSG-compliant it may be uploaded to
9137 the <em>contrib</em> distribution. While known existing
9138 versions of Motif permit unlimited redistribution of
9139 binaries linked against the library (whether statically or
9140 dynamically), it is the package maintainer's
9141 responsibility to determine whether this is permitted by
9142 the license of the copy of Motif in their possession.
9148 <heading>Perl programs and modules</heading>
9151 Perl programs and modules should follow the current Perl policy.
9155 The Perl policy can be found in the <tt>perl-policy</tt>
9156 files in the <tt>debian-policy</tt> package.
9157 It is also available from the Debian web mirrors at
9158 <tt><url name="/doc/packaging-manuals/perl-policy/"
9159 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9164 <heading>Emacs lisp programs</heading>
9167 Please refer to the "Debian Emacs Policy" for details of how to
9168 package emacs lisp programs.
9172 The Emacs policy is available in
9173 <file>debian-emacs-policy.gz</file> of the
9174 <package>emacsen-common</package> package.
9175 It is also available from the Debian web mirrors at
9176 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9177 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9182 <heading>Games</heading>
9185 The permissions on <file>/var/games</file> are mode 755, owner
9186 <tt>root</tt> and group <tt>root</tt>.
9190 Each game decides on its own security policy.</p>
9193 Games which require protected, privileged access to
9194 high-score files, saved games, etc., may be made
9195 set-<em>group</em>-id (mode 2755) and owned by
9196 <tt>root:games</tt>, and use files and directories with
9197 appropriate permissions (770 <tt>root:games</tt>, for
9198 example). They must not be made
9199 set-<em>user</em>-id, as this causes security problems. (If
9200 an attacker can subvert any set-user-id game they can
9201 overwrite the executable of any other, causing other players
9202 of these games to run a Trojan horse program. With a
9203 set-group-id game the attacker only gets access to less
9204 important game data, and if they can get at the other
9205 players' accounts at all it will take considerably more
9209 Some packages, for example some fortune cookie programs, are
9210 configured by the upstream authors to install with their
9211 data files or other static information made unreadable so
9212 that they can only be accessed through set-id programs
9213 provided. You should not do this in a Debian package: anyone can
9214 download the <file>.deb</file> file and read the data from it,
9215 so there is no point making the files unreadable. Not
9216 making the files unreadable also means that you don't have
9217 to make so many programs set-id, which reduces the risk of a
9221 As described in the FHS, binaries of games should be
9222 installed in the directory <file>/usr/games</file>. This also
9223 applies to games that use the X Window System. Manual pages
9224 for games (X and non-X games) should be installed in
9225 <file>/usr/share/man/man6</file>.</p>
9231 <heading>Documentation</heading>
9234 <heading>Manual pages</heading>
9237 You should install manual pages in <prgn>nroff</prgn> source
9238 form, in appropriate places under <file>/usr/share/man</file>.
9239 You should only use sections 1 to 9 (see the FHS for more
9240 details). You must not install a pre-formatted "cat page".
9244 Each program, utility, and function should have an
9245 associated manual page included in the same package. It is
9246 suggested that all configuration files also have a manual
9247 page included as well. Manual pages for protocols and other
9248 auxiliary things are optional.
9252 If no manual page is available, this is considered as a bug
9253 and should be reported to the Debian Bug Tracking System (the
9254 maintainer of the package is allowed to write this bug report
9255 themselves, if they so desire). Do not close the bug report
9256 until a proper man page is available.<footnote>
9257 It is not very hard to write a man page. See the
9258 <url id="http://www.schweikhardt.net/man_page_howto.html"
9259 name="Man-Page-HOWTO">,
9260 <manref name="man" section="7">, the examples
9261 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9262 the helper program <prgn>help2man</prgn>, or the
9263 directory <file>/usr/share/doc/man-db/examples</file>.
9268 You may forward a complaint about a missing man page to the
9269 upstream authors, and mark the bug as forwarded in the
9270 Debian bug tracking system. Even though the GNU Project do
9271 not in general consider the lack of a man page to be a bug,
9272 we do; if they tell you that they don't consider it a bug
9273 you should leave the bug in our bug tracking system open
9278 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9282 If one man page needs to be accessible via several names it
9283 is better to use a symbolic link than the <file>.so</file>
9284 feature, but there is no need to fiddle with the relevant
9285 parts of the upstream source to change from <file>.so</file> to
9286 symlinks: don't do it unless it's easy. You should not
9287 create hard links in the manual page directories, nor put
9288 absolute filenames in <file>.so</file> directives. The filename
9289 in a <file>.so</file> in a man page should be relative to the
9290 base of the man page tree (usually
9291 <file>/usr/share/man</file>). If you do not create any links
9292 (whether symlinks, hard links, or <tt>.so</tt> directives)
9293 in the file system to the alternate names of the man page,
9294 then you should not rely on <prgn>man</prgn> finding your
9295 man page under those names based solely on the information in
9296 the man page's header.<footnote>
9297 Supporting this in <prgn>man</prgn> often requires
9298 unreasonable processing time to find a manual page or to
9299 report that none exists, and moves knowledge into man's
9300 database that would be better left in the file system.
9301 This support is therefore deprecated and will cease to
9302 be present in the future.
9307 Manual pages in locale-specific subdirectories of
9308 <file>/usr/share/man</file> should use either UTF-8 or the usual
9309 legacy encoding for that language (normally the one corresponding
9310 to the shortest relevant locale name in
9311 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9312 <file>/usr/share/man/fr</file> should use either UTF-8 or
9313 ISO-8859-1.<footnote>
9314 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9315 use. In future, all manual pages will be required to use
9321 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9322 included in the subdirectory name unless it indicates a
9323 significant difference in the language, as this excludes
9324 speakers of the language in other countries.<footnote>
9325 At the time of writing, Chinese and Portuguese are the main
9326 languages with such differences, so <file>pt_BR</file>,
9327 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9332 If a localized version of a manual page is provided, it should
9333 either be up-to-date or it should be obvious to the reader that
9334 it is outdated and the original manual page should be used
9335 instead. This can be done either by a note at the beginning of
9336 the manual page or by showing the missing or changed portions in
9337 the original language instead of the target language.
9342 <heading>Info documents</heading>
9345 Info documents should be installed in <file>/usr/share/info</file>.
9346 They should be compressed with <tt>gzip -9</tt>.
9350 The <prgn>install-info</prgn> program maintains a directory of
9351 installed info documents in <file>/usr/share/info/dir</file> for
9352 the use of info readers.<footnote>
9353 It was previously necessary for packages installing info
9354 documents to run <prgn>install-info</prgn> from maintainer
9355 scripts. This is no longer necessary. The installation
9356 system now uses dpkg triggers.
9358 This file must not be included in packages. Packages containing
9359 info documents should depend on <tt>dpkg (>= 1.15.4) |
9360 install-info</tt> to ensure that the directory file is properly
9361 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9366 Info documents should contain section and directory entry
9367 information in the document for the use
9368 of <prgn>install-info</prgn>. The section should be specified
9369 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9370 space and the section of this info page. The directory entry or
9371 entries should be included between
9372 a <tt>START-INFO-DIR-ENTRY</tt> line and
9373 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9375 INFO-DIR-SECTION Individual utilities
9376 START-INFO-DIR-ENTRY
9377 * example: (example). An example info directory entry.
9380 To determine which section to use, you should look
9381 at <file>/usr/share/info/dir</file> on your system and choose
9382 the most relevant (or create a new section if none of the
9383 current sections are relevant).<footnote>
9384 Normally, info documents are generated from Texinfo source.
9385 To include this information in the generated info document, if
9386 it is absent, add commands like:
9388 @dircategory Individual utilities
9390 * example: (example). An example info directory entry.
9393 to the Texinfo source of the document and ensure that the info
9394 documents are rebuilt from source during the package build.
9400 <heading>Additional documentation</heading>
9403 Any additional documentation that comes with the package may
9404 be installed at the discretion of the package maintainer.
9405 Plain text documentation should be installed in the directory
9406 <file>/usr/share/doc/<var>package</var></file>, where
9407 <var>package</var> is the name of the package, and
9408 compressed with <tt>gzip -9</tt> unless it is small.
9412 If a package comes with large amounts of documentation which
9413 many users of the package will not require you should create
9414 a separate binary package to contain it, so that it does not
9415 take up disk space on the machines of users who do not need
9416 or want it installed.</p>
9419 It is often a good idea to put text information files
9420 (<file>README</file>s, changelogs, and so forth) that come with
9421 the source package in <file>/usr/share/doc/<var>package</var></file>
9422 in the binary package. However, you don't need to install
9423 the instructions for building and installing the package, of
9427 Packages must not require the existence of any files in
9428 <file>/usr/share/doc/</file> in order to function
9430 The system administrator should be able to
9431 delete files in <file>/usr/share/doc/</file> without causing
9432 any programs to break.
9434 Any files that are referenced by programs but are also
9435 useful as stand alone documentation should be installed under
9436 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9437 <file>/usr/share/doc/<var>package</var></file>.
9441 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9442 link to another directory in <file>/usr/share/doc</file> only if
9443 the two packages both come from the same source and the
9444 first package Depends on the second.<footnote>
9446 Please note that this does not override the section on
9447 changelog files below, so the file
9448 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9449 must refer to the changelog for the current version of
9450 <var>package</var> in question. In practice, this means
9451 that the sources of the target and the destination of the
9452 symlink must be the same (same source package and
9459 Former Debian releases placed all additional documentation
9460 in <file>/usr/doc/<var>package</var></file>. This has been
9461 changed to <file>/usr/share/doc/<var>package</var></file>,
9462 and packages must not put documentation in the directory
9463 <file>/usr/doc/<var>package</var></file>. <footnote>
9464 At this phase of the transition, we no longer require a
9465 symbolic link in <file>/usr/doc/</file>. At a later point,
9466 policy shall change to make the symbolic links a bug.
9472 <heading>Preferred documentation formats</heading>
9475 The unification of Debian documentation is being carried out
9479 If your package comes with extensive documentation in a
9480 markup format that can be converted to various other formats
9481 you should if possible ship HTML versions in a binary
9482 package, in the directory
9483 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9484 its subdirectories.<footnote>
9485 The rationale: The important thing here is that HTML
9486 docs should be available in <em>some</em> package, not
9487 necessarily in the main binary package.
9492 Other formats such as PostScript may be provided at the
9493 package maintainer's discretion.
9497 <sect id="copyrightfile">
9498 <heading>Copyright information</heading>
9501 Every package must be accompanied by a verbatim copy of its
9502 copyright information and distribution license in the file
9503 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9504 file must neither be compressed nor be a symbolic link.
9508 In addition, the copyright file must say where the upstream
9509 sources (if any) were obtained. It should name the original
9510 authors of the package and the Debian maintainer(s) who were
9511 involved with its creation.
9515 Packages in the <em>contrib</em> or <em>non-free</em> archive
9516 areas should state in the copyright file that the package is not
9517 part of the Debian GNU/Linux distribution and briefly explain
9522 A copy of the file which will be installed in
9523 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9524 be in <file>debian/copyright</file> in the source package.
9528 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9529 link to another directory in <file>/usr/share/doc</file> only if
9530 the two packages both come from the same source and the
9531 first package Depends on the second. These rules are
9532 important because copyrights must be extractable by
9537 Packages distributed under the Apache license (version 2.0), the
9538 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9539 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9540 1.3) should refer to the corresponding files
9541 under <file>/usr/share/common-licenses</file>,<footnote>
9544 <file>/usr/share/common-licenses/Apache-2.0</file>,
9545 <file>/usr/share/common-licenses/Artistic</file>,
9546 <file>/usr/share/common-licenses/GPL-1</file>,
9547 <file>/usr/share/common-licenses/GPL-2</file>,
9548 <file>/usr/share/common-licenses/GPL-3</file>,
9549 <file>/usr/share/common-licenses/LGPL-2</file>,
9550 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9551 <file>/usr/share/common-licenses/LGPL-3</file>,
9552 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9553 <file>/usr/share/common-licenses/GFDL-1.3</file>
9554 respectively. The University of California BSD license is
9555 also included in <package>base-files</package> as
9556 <file>/usr/share/common-licenses/BSD</file>, but given the
9557 brevity of this license, its specificity to code whose
9558 copyright is held by the Regents of the University of
9559 California, and the frequency of minor wording changes, its
9560 text should be included in the copyright file rather than
9561 referencing this file.
9563 </footnote> rather than quoting them in the copyright
9568 You should not use the copyright file as a general <file>README</file>
9569 file. If your package has such a file it should be
9570 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9571 <file>README.Debian</file> or some other appropriate place.</p>
9575 <heading>Examples</heading>
9578 Any examples (configurations, source files, whatever),
9579 should be installed in a directory
9580 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9581 files should not be referenced by any program: they're there
9582 for the benefit of the system administrator and users as
9583 documentation only. Architecture-specific example files
9584 should be installed in a directory
9585 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9587 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9588 latter directory itself may be a symbolic link to the
9593 If the purpose of a package is to provide examples, then the
9594 example files may be installed into
9595 <file>/usr/share/doc/<var>package</var></file>.
9599 <sect id="changelogs">
9600 <heading>Changelog files</heading>
9603 Packages that are not Debian-native must contain a
9604 compressed copy of the <file>debian/changelog</file> file from
9605 the Debian source tree in
9606 <file>/usr/share/doc/<var>package</var></file> with the name
9607 <file>changelog.Debian.gz</file>.
9611 If an upstream changelog is available, it should be accessible as
9612 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9613 plain text. If the upstream changelog is distributed in
9614 HTML, it should be made available in that form as
9615 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9616 and a plain text <file>changelog.gz</file> should be generated
9617 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9618 the upstream changelog files do not already conform to this
9619 naming convention, then this may be achieved either by
9620 renaming the files, or by adding a symbolic link, at the
9621 maintainer's discretion.<footnote>
9622 Rationale: People should not have to look in places for
9623 upstream changelogs merely because they are given
9624 different names or are distributed in HTML format.
9629 All of these files should be installed compressed using
9630 <tt>gzip -9</tt>, as they will become large with time even
9631 if they start out small.
9635 If the package has only one changelog which is used both as
9636 the Debian changelog and the upstream one because there is
9637 no separate upstream maintainer then that changelog should
9638 usually be installed as
9639 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9640 there is a separate upstream maintainer, but no upstream
9641 changelog, then the Debian changelog should still be called
9642 <file>changelog.Debian.gz</file>.
9646 For details about the format and contents of the Debian
9647 changelog file, please see <ref id="dpkgchangelog">.
9652 <appendix id="pkg-scope">
9653 <heading>Introduction and scope of these appendices</heading>
9656 These appendices are taken essentially verbatim from the
9657 now-deprecated Packaging Manual, version 3.2.1.0. They are
9658 the chapters which are likely to be of use to package
9659 maintainers and which have not already been included in the
9660 policy document itself. Most of these sections are very likely
9661 not relevant to policy; they should be treated as
9662 documentation for the packaging system. Please note that these
9663 appendices are included for convenience, and for historical
9664 reasons: they used to be part of policy package, and they have
9665 not yet been incorporated into dpkg documentation. However,
9666 they still have value, and hence they are presented here.
9670 They have not yet been checked to ensure that they are
9671 compatible with the contents of policy, and if there are any
9672 contradictions, the version in the main policy document takes
9673 precedence. The remaining chapters of the old Packaging
9674 Manual have also not been read in detail to ensure that there
9675 are not parts which have been left out. Both of these will be
9680 Certain parts of the Packaging manual were integrated into the
9681 Policy Manual proper, and removed from the appendices. Links
9682 have been placed from the old locations to the new ones.
9686 <prgn>dpkg</prgn> is a suite of programs for creating binary
9687 package files and installing and removing them on Unix
9689 <prgn>dpkg</prgn> is targeted primarily at Debian
9690 GNU/Linux, but may work on or be ported to other
9696 The binary packages are designed for the management of
9697 installed executable programs (usually compiled binaries) and
9698 their associated data, though source code examples and
9699 documentation are provided as part of some packages.</p>
9702 This manual describes the technical aspects of creating Debian
9703 binary packages (<file>.deb</file> files). It documents the
9704 behavior of the package management programs
9705 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9706 they interact with packages.</p>
9709 It also documents the interaction between
9710 <prgn>dselect</prgn>'s core and the access method scripts it
9711 uses to actually install the selected packages, and describes
9712 how to create a new access method.</p>
9715 This manual does not go into detail about the options and
9716 usage of the package building and installation tools. It
9717 should therefore be read in conjunction with those programs'
9722 The utility programs which are provided with <prgn>dpkg</prgn>
9723 for managing various system configuration and similar issues,
9724 such as <prgn>update-rc.d</prgn> and
9725 <prgn>install-info</prgn>, are not described in detail here -
9726 please see their man pages.
9730 It is assumed that the reader is reasonably familiar with the
9731 <prgn>dpkg</prgn> System Administrators' manual.
9732 Unfortunately this manual does not yet exist.
9736 The Debian version of the FSF's GNU hello program is provided
9737 as an example for people wishing to create Debian
9738 packages. The Debian <prgn>debmake</prgn> package is
9739 recommended as a very helpful tool in creating and maintaining
9740 Debian packages. However, while the tools and examples are
9741 helpful, they do not replace the need to read and follow the
9742 Policy and Programmer's Manual.</p>
9745 <appendix id="pkg-binarypkg">
9746 <heading>Binary packages (from old Packaging Manual)</heading>
9749 The binary package has two main sections. The first part
9750 consists of various control information files and scripts used
9751 by <prgn>dpkg</prgn> when installing and removing. See <ref
9752 id="pkg-controlarea">.
9756 The second part is an archive containing the files and
9757 directories to be installed.
9761 In the future binary packages may also contain other
9762 components, such as checksums and digital signatures. The
9763 format for the archive is described in full in the
9764 <file>deb(5)</file> man page.
9768 <sect id="pkg-bincreating"><heading>Creating package files -
9769 <prgn>dpkg-deb</prgn>
9773 All manipulation of binary package files is done by
9774 <prgn>dpkg-deb</prgn>; it's the only program that has
9775 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9776 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9777 will spot that the options requested are appropriate to
9778 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9783 In order to create a binary package you must make a
9784 directory tree which contains all the files and directories
9785 you want to have in the file system data part of the package.
9786 In Debian-format source packages this directory is usually
9787 <file>debian/tmp</file>, relative to the top of the package's
9792 They should have the locations (relative to the root of the
9793 directory tree you're constructing) ownerships and
9794 permissions which you want them to have on the system when
9799 With current versions of <prgn>dpkg</prgn> the uid/username
9800 and gid/groupname mappings for the users and groups being
9801 used should be the same on the system where the package is
9802 built and the one where it is installed.
9806 You need to add one special directory to the root of the
9807 miniature file system tree you're creating:
9808 <prgn>DEBIAN</prgn>. It should contain the control
9809 information files, notably the binary package control file
9810 (see <ref id="pkg-controlfile">).
9814 The <prgn>DEBIAN</prgn> directory will not appear in the
9815 file system archive of the package, and so won't be installed
9816 by <prgn>dpkg</prgn> when the package is installed.
9820 When you've prepared the package, you should invoke:
9822 dpkg --build <var>directory</var>
9827 This will build the package in
9828 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9829 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9830 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9835 See the man page <manref name="dpkg-deb" section="8"> for details of how
9836 to examine the contents of this newly-created file. You may find the
9837 output of following commands enlightening:
9839 dpkg-deb --info <var>filename</var>.deb
9840 dpkg-deb --contents <var>filename</var>.deb
9841 dpkg --contents <var>filename</var>.deb
9843 To view the copyright file for a package you could use this command:
9845 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9850 <sect id="pkg-controlarea">
9851 <heading>Package control information files</heading>
9854 The control information portion of a binary package is a
9855 collection of files with names known to <prgn>dpkg</prgn>.
9856 It will treat the contents of these files specially - some
9857 of them contain information used by <prgn>dpkg</prgn> when
9858 installing or removing the package; others are scripts which
9859 the package maintainer wants <prgn>dpkg</prgn> to run.
9863 It is possible to put other files in the package control
9864 information file area, but this is not generally a good idea
9865 (though they will largely be ignored).
9869 Here is a brief list of the control information files supported
9870 by <prgn>dpkg</prgn> and a summary of what they're used for.
9875 <tag><tt>control</tt>
9878 This is the key description file used by
9879 <prgn>dpkg</prgn>. It specifies the package's name
9880 and version, gives its description for the user,
9881 states its relationships with other packages, and so
9882 forth. See <ref id="sourcecontrolfiles"> and
9883 <ref id="binarycontrolfiles">.
9887 It is usually generated automatically from information
9888 in the source package by the
9889 <prgn>dpkg-gencontrol</prgn> program, and with
9890 assistance from <prgn>dpkg-shlibdeps</prgn>.
9891 See <ref id="pkg-sourcetools">.
9895 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9900 These are executable files (usually scripts) which
9901 <prgn>dpkg</prgn> runs during installation, upgrade
9902 and removal of packages. They allow the package to
9903 deal with matters which are particular to that package
9904 or require more complicated processing than that
9905 provided by <prgn>dpkg</prgn>. Details of when and
9906 how they are called are in <ref id="maintainerscripts">.
9910 It is very important to make these scripts idempotent.
9911 See <ref id="idempotency">.
9915 The maintainer scripts are not guaranteed to run with a
9916 controlling terminal and may not be able to interact with
9917 the user. See <ref id="controllingterminal">.
9921 <tag><tt>conffiles</tt>
9924 This file contains a list of configuration files which
9925 are to be handled automatically by <prgn>dpkg</prgn>
9926 (see <ref id="pkg-conffiles">). Note that not necessarily
9927 every configuration file should be listed here.
9930 <tag><tt>shlibs</tt>
9933 This file contains a list of the shared libraries
9934 supplied by the package, with dependency details for
9935 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9936 when it determines what dependencies are required in a
9937 package control file. The <tt>shlibs</tt> file format
9938 is described on <ref id="shlibs">.
9943 <sect id="pkg-controlfile">
9944 <heading>The main control information file: <tt>control</tt></heading>
9947 The most important control information file used by
9948 <prgn>dpkg</prgn> when it installs a package is
9949 <tt>control</tt>. It contains all the package's "vital
9954 The binary package control files of packages built from
9955 Debian sources are made by a special tool,
9956 <prgn>dpkg-gencontrol</prgn>, which reads
9957 <file>debian/control</file> and <file>debian/changelog</file> to
9958 find the information it needs. See <ref id="pkg-sourcepkg"> for
9963 The fields in binary package control files are listed in
9964 <ref id="binarycontrolfiles">.
9968 A description of the syntax of control files and the purpose
9969 of the fields is available in <ref id="controlfields">.
9974 <heading>Time Stamps</heading>
9977 See <ref id="timestamps">.
9982 <appendix id="pkg-sourcepkg">
9983 <heading>Source packages (from old Packaging Manual) </heading>
9986 The Debian binary packages in the distribution are generated
9987 from Debian sources, which are in a special format to assist
9988 the easy and automatic building of binaries.
9991 <sect id="pkg-sourcetools">
9992 <heading>Tools for processing source packages</heading>
9995 Various tools are provided for manipulating source packages;
9996 they pack and unpack sources and help build of binary
9997 packages and help manage the distribution of new versions.
10001 They are introduced and typical uses described here; see
10002 <manref name="dpkg-source" section="1"> for full
10003 documentation about their arguments and operation.
10007 For examples of how to construct a Debian source package,
10008 and how to use those utilities that are used by Debian
10009 source packages, please see the <prgn>hello</prgn> example
10013 <sect1 id="pkg-dpkg-source">
10015 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10020 This program is frequently used by hand, and is also
10021 called from package-independent automated building scripts
10022 such as <prgn>dpkg-buildpackage</prgn>.
10026 To unpack a package it is typically invoked with
10028 dpkg-source -x <var>.../path/to/filename</var>.dsc
10033 with the <file><var>filename</var>.tar.gz</file> and
10034 <file><var>filename</var>.diff.gz</file> (if applicable) in
10035 the same directory. It unpacks into
10036 <file><var>package</var>-<var>version</var></file>, and if
10038 <file><var>package</var>-<var>version</var>.orig</file>, in
10039 the current directory.
10043 To create a packed source archive it is typically invoked:
10045 dpkg-source -b <var>package</var>-<var>version</var>
10050 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10051 <file>.diff.gz</file> (if appropriate) in the current
10052 directory. <prgn>dpkg-source</prgn> does not clean the
10053 source tree first - this must be done separately if it is
10058 See also <ref id="pkg-sourcearchives">.</p>
10062 <sect1 id="pkg-dpkg-buildpackage">
10064 <prgn>dpkg-buildpackage</prgn> - overall package-building
10069 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10070 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10071 targets <tt>clean</tt>, <tt>build</tt> and
10072 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10073 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10074 source and binary package upload.
10078 It is usually invoked by hand from the top level of the
10079 built or unbuilt source directory. It may be invoked with
10080 no arguments; useful arguments include:
10081 <taglist compact="compact">
10082 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10085 Do not sign the <tt>.changes</tt> file or the
10086 source package <tt>.dsc</tt> file, respectively.</p>
10088 <tag><tt>-p<var>sign-command</var></tt></tag>
10091 Invoke <var>sign-command</var> instead of finding
10092 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10093 <var>sign-command</var> must behave just like
10094 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10096 <tag><tt>-r<var>root-command</var></tt></tag>
10099 When root privilege is required, invoke the command
10100 <var>root-command</var>. <var>root-command</var>
10101 should invoke its first argument as a command, from
10102 the <prgn>PATH</prgn> if necessary, and pass its
10103 second and subsequent arguments to the command it
10104 calls. If no <var>root-command</var> is supplied
10105 then <var>dpkg-buildpackage</var> will take no
10106 special action to gain root privilege, so that for
10107 most packages it will have to be invoked as root to
10110 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10113 Two types of binary-only build and upload - see
10114 <manref name="dpkg-source" section="1">.
10121 <sect1 id="pkg-dpkg-gencontrol">
10123 <prgn>dpkg-gencontrol</prgn> - generates binary package
10128 This program is usually called from <file>debian/rules</file>
10129 (see <ref id="pkg-sourcetree">) in the top level of the source
10134 This is usually done just before the files and directories in the
10135 temporary directory tree where the package is being built have their
10136 permissions and ownerships set and the package is constructed using
10137 <prgn>dpkg-deb/</prgn>
10139 This is so that the control file which is produced has
10140 the right permissions
10145 <prgn>dpkg-gencontrol</prgn> must be called after all the
10146 files which are to go into the package have been placed in
10147 the temporary build directory, so that its calculation of
10148 the installed size of a package is correct.
10152 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10153 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10154 variable substitutions created by
10155 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10160 For a package which generates only one binary package, and
10161 which builds it in <file>debian/tmp</file> relative to the top
10162 of the source package, it is usually sufficient to call
10163 <prgn>dpkg-gencontrol</prgn>.
10167 Sources which build several binaries will typically need
10170 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10171 </example> The <tt>-P</tt> tells
10172 <prgn>dpkg-gencontrol</prgn> that the package is being
10173 built in a non-default directory, and the <tt>-p</tt>
10174 tells it which package's control file should be generated.
10178 <prgn>dpkg-gencontrol</prgn> also adds information to the
10179 list of files in <file>debian/files</file>, for the benefit of
10180 (for example) a future invocation of
10181 <prgn>dpkg-genchanges</prgn>.</p>
10184 <sect1 id="pkg-dpkg-shlibdeps">
10186 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10191 This program is usually called from <file>debian/rules</file>
10192 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10193 id="pkg-sourcetree">), in the top level of the source tree.
10197 Its arguments are executables and shared libraries
10200 They may be specified either in the locations in the
10201 source tree where they are created or in the locations
10202 in the temporary build tree where they are installed
10203 prior to binary package creation.
10205 </footnote> for which shared library dependencies should
10206 be included in the binary package's control file.
10210 If some of the found shared libraries should only
10211 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10212 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10213 by using the <tt>-d<var>dependency-field</var></tt> option
10214 before those executable(s). (Each <tt>-d</tt> option
10215 takes effect until the next <tt>-d</tt>.)
10219 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10220 output control file to be modified. Instead by default it
10221 adds to the <file>debian/substvars</file> file variable
10222 settings like <tt>shlibs:Depends</tt>. These variable
10223 settings must be referenced in dependency fields in the
10224 appropriate per-binary-package sections of the source
10229 For example, a package that generates an essential part
10230 which requires dependencies, and optional parts that
10231 which only require a recommendation, would separate those
10232 two sets of dependencies into two different fields.<footnote>
10233 At the time of writing, an example for this was the
10234 <package/xmms/ package, with Depends used for the xmms
10235 executable, Recommends for the plug-ins and Suggests for
10236 even more optional features provided by unzip.
10238 It can say in its <file>debian/rules</file>:
10240 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10241 -dRecommends <var>optionalpart anotheroptionalpart</var>
10243 and then in its main control file <file>debian/control</file>:
10246 Depends: ${shlibs:Depends}
10247 Recommends: ${shlibs:Recommends}
10253 Sources which produce several binary packages with
10254 different shared library dependency requirements can use
10255 the <tt>-p<var>varnameprefix</var></tt> option to override
10256 the default <tt>shlibs:</tt> prefix (one invocation of
10257 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10258 They can thus produce several sets of dependency
10259 variables, each of the form
10260 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10261 which can be referred to in the appropriate parts of the
10262 binary package control files.
10267 <sect1 id="pkg-dpkg-distaddfile">
10269 <prgn>dpkg-distaddfile</prgn> - adds a file to
10270 <file>debian/files</file>
10274 Some packages' uploads need to include files other than
10275 the source and binary package files.
10279 <prgn>dpkg-distaddfile</prgn> adds a file to the
10280 <file>debian/files</file> file so that it will be included in
10281 the <file>.changes</file> file when
10282 <prgn>dpkg-genchanges</prgn> is run.
10286 It is usually invoked from the <tt>binary</tt> target of
10287 <file>debian/rules</file>:
10289 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10291 The <var>filename</var> is relative to the directory where
10292 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10293 is usually the directory above the top level of the source
10294 tree. The <file>debian/rules</file> target should put the
10295 file there just before or just after calling
10296 <prgn>dpkg-distaddfile</prgn>.
10300 The <var>section</var> and <var>priority</var> are passed
10301 unchanged into the resulting <file>.changes</file> file.
10306 <sect1 id="pkg-dpkg-genchanges">
10308 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10309 upload control file
10313 This program is usually called by package-independent
10314 automatic building scripts such as
10315 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10320 It is usually called in the top level of a built source
10321 tree, and when invoked with no arguments will print out a
10322 straightforward <file>.changes</file> file based on the
10323 information in the source package's changelog and control
10324 file and the binary and source packages which should have
10330 <sect1 id="pkg-dpkg-parsechangelog">
10332 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10333 representation of a changelog
10337 This program is used internally by
10338 <prgn>dpkg-source</prgn> et al. It may also occasionally
10339 be useful in <file>debian/rules</file> and elsewhere. It
10340 parses a changelog, <file>debian/changelog</file> by default,
10341 and prints a control-file format representation of the
10342 information in it to standard output.
10346 <sect1 id="pkg-dpkg-architecture">
10348 <prgn>dpkg-architecture</prgn> - information about the build and
10353 This program can be used manually, but is also invoked by
10354 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10355 environment or make variables which specify the build and host
10356 architecture for the package building process.
10361 <sect id="pkg-sourcetree">
10362 <heading>The Debian package source tree</heading>
10365 The source archive scheme described later is intended to
10366 allow a Debian package source tree with some associated
10367 control information to be reproduced and transported easily.
10368 The Debian package source tree is a version of the original
10369 program with certain files added for the benefit of the
10370 packaging process, and with any other changes required
10371 made to the rest of the source code and installation
10376 The extra files created for Debian are in the subdirectory
10377 <file>debian</file> of the top level of the Debian package
10378 source tree. They are described below.
10381 <sect1 id="pkg-debianrules">
10382 <heading><file>debian/rules</file> - the main building script</heading>
10385 See <ref id="debianrules">.
10389 <sect1 id="pkg-srcsubstvars">
10390 <heading><file>debian/substvars</file> and variable substitutions</heading>
10393 See <ref id="substvars">.
10399 <heading><file>debian/files</file></heading>
10402 See <ref id="debianfiles">.
10406 <sect1><heading><file>debian/tmp</file>
10410 This is the canonical temporary location for the
10411 construction of binary packages by the <tt>binary</tt>
10412 target. The directory <file>tmp</file> serves as the root of
10413 the file system tree as it is being constructed (for
10414 example, by using the package's upstream makefiles install
10415 targets and redirecting the output there), and it also
10416 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10417 id="pkg-bincreating">.
10421 If several binary packages are generated from the same
10422 source tree it is usual to use several
10423 <file>debian/tmp<var>something</var></file> directories, for
10424 example <file>tmp-a</file> or <file>tmp-doc</file>.
10428 Whatever <file>tmp</file> directories are created and used by
10429 <tt>binary</tt> must of course be removed by the
10430 <tt>clean</tt> target.</p></sect1>
10434 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10438 As it exists on the FTP site, a Debian source package
10439 consists of three related files. You must have the right
10440 versions of all three to be able to use them.
10445 <tag>Debian source control file - <tt>.dsc</tt></tag>
10447 This file is a control file used by <prgn>dpkg-source</prgn>
10448 to extract a source package.
10449 See <ref id="debiansourcecontrolfiles">.
10453 Original source archive -
10455 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10461 This is a compressed (with <tt>gzip -9</tt>)
10462 <prgn>tar</prgn> file containing the source code from
10463 the upstream authors of the program.
10468 Debian package diff -
10470 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10476 This is a unified context diff (<tt>diff -u</tt>)
10477 giving the changes which are required to turn the
10478 original source into the Debian source. These changes
10479 may only include editing and creating plain files.
10480 The permissions of files, the targets of symbolic
10481 links and the characteristics of special files or
10482 pipes may not be changed and no files may be removed
10487 All the directories in the diff must exist, except the
10488 <file>debian</file> subdirectory of the top of the source
10489 tree, which will be created by
10490 <prgn>dpkg-source</prgn> if necessary when unpacking.
10494 The <prgn>dpkg-source</prgn> program will
10495 automatically make the <file>debian/rules</file> file
10496 executable (see below).</p></item>
10501 If there is no original source code - for example, if the
10502 package is specially prepared for Debian or the Debian
10503 maintainer is the same as the upstream maintainer - the
10504 format is slightly different: then there is no diff, and the
10506 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10507 and preferably contains a directory named
10508 <file><var>package</var>-<var>version</var></file>.
10513 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10516 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10517 Debian source package. However, if it is not available it
10518 is possible to unpack a Debian source archive as follows:
10519 <enumlist compact="compact">
10522 Untar the tarfile, which will create a <file>.orig</file>
10526 <p>Rename the <file>.orig</file> directory to
10527 <file><var>package</var>-<var>version</var></file>.</p>
10531 Create the subdirectory <file>debian</file> at the top of
10532 the source tree.</p>
10534 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10536 <item><p>Untar the tarfile again if you want a copy of the original
10537 source code alongside the Debian version.</p>
10542 It is not possible to generate a valid Debian source archive
10543 without using <prgn>dpkg-source</prgn>. In particular,
10544 attempting to use <prgn>diff</prgn> directly to generate the
10545 <file>.diff.gz</file> file will not work.
10549 <heading>Restrictions on objects in source packages</heading>
10552 The source package may not contain any hard links
10554 This is not currently detected when building source
10555 packages, but only when extracting
10559 Hard links may be permitted at some point in the
10560 future, but would require a fair amount of
10562 </footnote>, device special files, sockets or setuid or
10565 Setgid directories are allowed.
10570 The source packaging tools manage the changes between the
10571 original and Debian source using <prgn>diff</prgn> and
10572 <prgn>patch</prgn>. Turning the original source tree as
10573 included in the <file>.orig.tar.gz</file> into the Debian
10574 package source must not involve any changes which cannot be
10575 handled by these tools. Problematic changes which cause
10576 <prgn>dpkg-source</prgn> to halt with an error when
10577 building the source package are:
10578 <list compact="compact">
10579 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10581 <item><p>Changing the targets of symbolic links.</p>
10583 <item><p>Creating directories, other than <file>debian</file>.</p>
10585 <item><p>Changes to the contents of binary files.</p></item>
10586 </list> Changes which cause <prgn>dpkg-source</prgn> to
10587 print a warning but continue anyway are:
10588 <list compact="compact">
10591 Removing files, directories or symlinks.
10593 Renaming a file is not treated specially - it is
10594 seen as the removal of the old file (which
10595 generates a warning, but is otherwise ignored),
10596 and the creation of the new one.
10602 Changed text files which are missing the usual final
10603 newline (either in the original or the modified
10608 Changes which are not represented, but which are not detected by
10609 <prgn>dpkg-source</prgn>, are:
10610 <list compact="compact">
10611 <item><p>Changing the permissions of files (other than
10612 <file>debian/rules</file>) and directories.</p></item>
10617 The <file>debian</file> directory and <file>debian/rules</file>
10618 are handled specially by <prgn>dpkg-source</prgn> - before
10619 applying the changes it will create the <file>debian</file>
10620 directory, and afterwards it will make
10621 <file>debian/rules</file> world-executable.
10627 <appendix id="pkg-controlfields">
10628 <heading>Control files and their fields (from old Packaging Manual)</heading>
10631 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10632 data in a common format, known as control files. Binary and
10633 source packages have control data as do the <file>.changes</file>
10634 files which control the installation of uploaded files, and
10635 <prgn>dpkg</prgn>'s internal databases are in a similar
10640 <heading>Syntax of control files</heading>
10643 See <ref id="controlsyntax">.
10647 It is important to note that there are several fields which
10648 are optional as far as <prgn>dpkg</prgn> and the related
10649 tools are concerned, but which must appear in every Debian
10650 package, or whose omission may cause problems.
10655 <heading>List of fields</heading>
10658 See <ref id="controlfieldslist">.
10662 This section now contains only the fields that didn't belong
10663 to the Policy manual.
10666 <sect1 id="pkg-f-Filename">
10667 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10670 These fields in <tt>Packages</tt> files give the
10671 filename(s) of (the parts of) a package in the
10672 distribution directories, relative to the root of the
10673 Debian hierarchy. If the package has been split into
10674 several parts the parts are all listed in order, separated
10679 <sect1 id="pkg-f-Size">
10680 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10683 These fields in <file>Packages</file> files give the size (in
10684 bytes, expressed in decimal) and MD5 checksum of the
10685 file(s) which make(s) up a binary package in the
10686 distribution. If the package is split into several parts
10687 the values for the parts are listed in order, separated by
10692 <sect1 id="pkg-f-Status">
10693 <heading><tt>Status</tt></heading>
10696 This field in <prgn>dpkg</prgn>'s status file records
10697 whether the user wants a package installed, removed or
10698 left alone, whether it is broken (requiring
10699 re-installation) or not and what its current state on the
10700 system is. Each of these pieces of information is a
10705 <sect1 id="pkg-f-Config-Version">
10706 <heading><tt>Config-Version</tt></heading>
10709 If a package is not installed or not configured, this
10710 field in <prgn>dpkg</prgn>'s status file records the last
10711 version of the package which was successfully
10716 <sect1 id="pkg-f-Conffiles">
10717 <heading><tt>Conffiles</tt></heading>
10720 This field in <prgn>dpkg</prgn>'s status file contains
10721 information about the automatically-managed configuration
10722 files held by a package. This field should <em>not</em>
10723 appear anywhere in a package!
10728 <heading>Obsolete fields</heading>
10731 These are still recognized by <prgn>dpkg</prgn> but should
10732 not appear anywhere any more.
10734 <taglist compact="compact">
10736 <tag><tt>Revision</tt></tag>
10737 <tag><tt>Package-Revision</tt></tag>
10738 <tag><tt>Package_Revision</tt></tag>
10740 The Debian revision part of the package version was
10741 at one point in a separate control field. This
10742 field went through several names.
10745 <tag><tt>Recommended</tt></tag>
10746 <item>Old name for <tt>Recommends</tt>.</item>
10748 <tag><tt>Optional</tt></tag>
10749 <item>Old name for <tt>Suggests</tt>.</item>
10751 <tag><tt>Class</tt></tag>
10752 <item>Old name for <tt>Priority</tt>.</item>
10761 <appendix id="pkg-conffiles">
10762 <heading>Configuration file handling (from old Packaging Manual)</heading>
10765 <prgn>dpkg</prgn> can do a certain amount of automatic
10766 handling of package configuration files.
10770 Whether this mechanism is appropriate depends on a number of
10771 factors, but basically there are two approaches to any
10772 particular configuration file.
10776 The easy method is to ship a best-effort configuration in the
10777 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10778 handle updates. If the user is unlikely to want to edit the
10779 file, but you need them to be able to without losing their
10780 changes, and a new package with a changed version of the file
10781 is only released infrequently, this is a good approach.
10785 The hard method is to build the configuration file from
10786 scratch in the <prgn>postinst</prgn> script, and to take the
10787 responsibility for fixing any mistakes made in earlier
10788 versions of the package automatically. This will be
10789 appropriate if the file is likely to need to be different on
10793 <sect><heading>Automatic handling of configuration files by
10798 A package may contain a control information file called
10799 <tt>conffiles</tt>. This file should be a list of filenames
10800 of configuration files needing automatic handling, separated
10801 by newlines. The filenames should be absolute pathnames,
10802 and the files referred to should actually exist in the
10807 When a package is upgraded <prgn>dpkg</prgn> will process
10808 the configuration files during the configuration stage,
10809 shortly before it runs the package's <prgn>postinst</prgn>
10814 For each file it checks to see whether the version of the
10815 file included in the package is the same as the one that was
10816 included in the last version of the package (the one that is
10817 being upgraded from); it also compares the version currently
10818 installed on the system with the one shipped with the last
10823 If neither the user nor the package maintainer has changed
10824 the file, it is left alone. If one or the other has changed
10825 their version, then the changed version is preferred - i.e.,
10826 if the user edits their file, but the package maintainer
10827 doesn't ship a different version, the user's changes will
10828 stay, silently, but if the maintainer ships a new version
10829 and the user hasn't edited it the new version will be
10830 installed (with an informative message). If both have
10831 changed their version the user is prompted about the problem
10832 and must resolve the differences themselves.
10836 The comparisons are done by calculating the MD5 message
10837 digests of the files, and storing the MD5 of the file as it
10838 was included in the most recent version of the package.
10842 When a package is installed for the first time
10843 <prgn>dpkg</prgn> will install the file that comes with it,
10844 unless that would mean overwriting a file already on the
10849 However, note that <prgn>dpkg</prgn> will <em>not</em>
10850 replace a conffile that was removed by the user (or by a
10851 script). This is necessary because with some programs a
10852 missing file produces an effect hard or impossible to
10853 achieve in another way, so that a missing file needs to be
10854 kept that way if the user did it.
10858 Note that a package should <em>not</em> modify a
10859 <prgn>dpkg</prgn>-handled conffile in its maintainer
10860 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10861 the user confusing and possibly dangerous options for
10862 conffile update when the package is upgraded.</p>
10865 <sect><heading>Fully-featured maintainer script configuration
10870 For files which contain site-specific information such as
10871 the hostname and networking details and so forth, it is
10872 better to create the file in the package's
10873 <prgn>postinst</prgn> script.
10877 This will typically involve examining the state of the rest
10878 of the system to determine values and other information, and
10879 may involve prompting the user for some information which
10880 can't be obtained some other way.
10884 When using this method there are a couple of important
10885 issues which should be considered:
10889 If you discover a bug in the program which generates the
10890 configuration file, or if the format of the file changes
10891 from one version to the next, you will have to arrange for
10892 the postinst script to do something sensible - usually this
10893 will mean editing the installed configuration file to remove
10894 the problem or change the syntax. You will have to do this
10895 very carefully, since the user may have changed the file,
10896 perhaps to fix the very problem that your script is trying
10897 to deal with - you will have to detect these situations and
10898 deal with them correctly.
10902 If you do go down this route it's probably a good idea to
10903 make the program that generates the configuration file(s) a
10904 separate program in <file>/usr/sbin</file>, by convention called
10905 <file><var>package</var>config</file> and then run that if
10906 appropriate from the post-installation script. The
10907 <tt><var>package</var>config</tt> program should not
10908 unquestioningly overwrite an existing configuration - if its
10909 mode of operation is geared towards setting up a package for
10910 the first time (rather than any arbitrary reconfiguration
10911 later) you should have it check whether the configuration
10912 already exists, and require a <tt>--force</tt> flag to
10913 overwrite it.</p></sect>
10916 <appendix id="pkg-alternatives"><heading>Alternative versions of
10917 an interface - <prgn>update-alternatives</prgn> (from old
10922 When several packages all provide different versions of the
10923 same program or file it is useful to have the system select a
10924 default, but to allow the system administrator to change it
10925 and have their decisions respected.
10929 For example, there are several versions of the <prgn>vi</prgn>
10930 editor, and there is no reason to prevent all of them from
10931 being installed at once, each under their own name
10932 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10933 Nevertheless it is desirable to have the name <tt>vi</tt>
10934 refer to something, at least by default.
10938 If all the packages involved cooperate, this can be done with
10939 <prgn>update-alternatives</prgn>.
10943 Each package provides its own version under its own name, and
10944 calls <prgn>update-alternatives</prgn> in its postinst to
10945 register its version (and again in its prerm to deregister
10950 See the man page <manref name="update-alternatives"
10951 section="8"> for details.
10955 If <prgn>update-alternatives</prgn> does not seem appropriate
10956 you may wish to consider using diversions instead.</p>
10959 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10960 package's version of a file (from old Packaging Manual)
10964 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10965 when it reinstalls the package it belongs to, and to have it
10966 put the file from the package somewhere else instead.
10970 This can be used locally to override a package's version of a
10971 file, or by one package to override another's version (or
10972 provide a wrapper for it).
10976 Before deciding to use a diversion, read <ref
10977 id="pkg-alternatives"> to see if you really want a diversion
10978 rather than several alternative versions of a program.
10982 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10983 and updated by a special program <prgn>dpkg-divert</prgn>.
10984 Please see <manref name="dpkg-divert" section="8"> for full
10985 details of its operation.
10989 When a package wishes to divert a file from another, it should
10990 call <prgn>dpkg-divert</prgn> in its preinst to add the
10991 diversion and rename the existing file. For example,
10992 supposing that a <prgn>smailwrapper</prgn> package wishes to
10993 install a wrapper around <file>/usr/sbin/smail</file>:
10995 dpkg-divert --package smailwrapper --add --rename \
10996 --divert /usr/sbin/smail.real /usr/sbin/smail
10997 </example> The <tt>--package smailwrapper</tt> ensures that
10998 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10999 can bypass the diversion and get installed as the true version.
11000 It's safe to add the diversion unconditionally on upgrades since
11001 it will be left unchanged if it already exists, but
11002 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11003 message, make the command conditional on the version from which
11004 the package is being upgraded:
11006 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11007 dpkg-divert --package smailwrapper --add --rename \
11008 --divert /usr/sbin/smail.real /usr/sbin/smail
11010 </example> where <tt>1.0-2</tt> is the version at which the
11011 diversion was first added to the package. Running the command
11012 during abort-upgrade is pointless but harmless.
11016 The postrm has to do the reverse:
11018 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11019 dpkg-divert --package smailwrapper --remove --rename \
11020 --divert /usr/sbin/smail.real /usr/sbin/smail
11022 </example> If the diversion was added at a particular version, the
11023 postrm should also handle the failure case of upgrading from an
11024 older version (unless the older version is so old that direct
11025 upgrades are no longer supported):
11027 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11028 dpkg-divert --package smailwrapper --remove --rename \
11029 --divert /usr/sbin/smail.real /usr/sbin/smail
11031 </example> where <tt>1.02-2</tt> is the version at which the
11032 diversion was first added to the package. The postrm should not
11033 remove the diversion on upgrades both because there's no reason to
11034 remove the diversion only to immediately re-add it and since the
11035 postrm of the old package is run after unpacking so the removal of
11036 the diversion will fail.
11040 Do not attempt to divert a file which is vitally important for
11041 the system's operation - when using <prgn>dpkg-divert</prgn>
11042 there is a time, after it has been diverted but before
11043 <prgn>dpkg</prgn> has installed the new version, when the file
11044 does not exist.</p>
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